Upgrade to CSS4J 0.40.3

Version 0.40.3
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 * Core:
- NSAC: add the flexible length unit (fr) numeric identifier to LexicalUnit2.
- NSAC: add lexical unit identifiers for left and right square brackets.
- NSAC implementation: support the flex (fr) unit.
- NSAC implementation: support square brackets in values.
- NSAC impl: document difference of behaviour of AttributeCondition2 vs SAC's 
  AttributeCondition.
- NSAC implementation: fix a bug processing comments ending with an asterisk.
- NSAC impl.: fix an issue parsing arguments in :not and :has pseudo-classes.
- NSAC LexicalUnit2: change 'q' by 'Q' in SAC_QUARTER_MILLIMETER.
- Remove deprecated getWidthSize(String) from StyleDatabase.
- CSSPrimitiveValue2: rename CSS_QUARTER_MILLIMETER to CSS_QUARTER_MM for 
  consistency.
- CSSOM: add missing level 4 units to CSSPrimitiveValue2.
- CSSOM: add identifier for flex (fr) values in CSSPrimitiveValue2.
- CSSOM: support bracket lists inside functions.
- CSSOM: fix an issue with some expressions embedded within calc() values.
- Add a test and a comment clarification for CSSOM calc() support.
- CSSOM: use an interface instead of a class in DeclarationCondition.
- ValueFactory: support for bracket lists and flex (fr) units.
- Add an iterator and addAll methods to OMCSSValueList.
- Have OMCSSFunctionValue's getStringValue() method return the function name.
- Support the 'column' shorthand.
- Support for the 'flex' shorthand.
- Support flex-flow shorthand.
- Support column-rule shorthand.
- Support place-content shorthand.
- Support for place-items shorthand property.
- Support grid, grid-template, grid-row, grid-column and grid-area shorthands.
- Support the 'gap' shorthand.
- Small improvement to border-* shorthand serialization.
- Identify functions with color arguments as valid colors in shorthands.
- Bug: have ValueFactory.isPositiveSizeSACUnit return false for non-positive 
  values.
- Bug: correctly identify bad mixed-keyword cases in some shorthands.
- Fix a bug in the border-image shorthand getCssText()
- AbstractCSSPrimitiveValue: set the subproperty field in the copy constructor.
- PropertyDatabase: add initial values for more grid properties.
- Add isNumberZero() to AbstractCSSPrimitiveValue.
- Avoid unnecessary method call in CSSStyleDeclarationRule.selectorText()
- Add initial values for a few additional properties.
- Update LICENSE.txt file location in headers.
- AnimationShorthandBuilder: put comment at the correct place.
- Improvements to javadoc comments.

Version 0.40.2
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 * Core:
- Remove getSelectorsForPropertyValue from ExtendedCSSStyleSheet, replacing it 
  with getSelectorsForProperty.
- Fix absolutization of computed calc() values.
- Support minified calc() values.
- Accept counter-styles in list-style shorthand.
- Filter additional potential bad names for @counter-style rules.
- In box shorthands, do not use supplied shorthand cssText if that could confuse 
  browsers.
- More consistent ordering for sub-properties of box shorthands, even when they 
  are unlikely to be displayed in cssText.
- Build safer border-color shorthands.
- CSSOM: support for 'animation' and latest spec changes in 'list-style'.
- CSSOM: introduce the CSSGroupingRule and CSSConditionRule interfaces.
- CSSOM: add abstract clone() to AbstractCSSValue (making it effectively 
  abstract).
- Have NodeStyleDeclaration extend CSSStyleDeclaration.
- Add hasKnownIdentifierValues to PropertyDatabase.
- Add sanity checks for building generic shorthands.
- Refactor the SheetErrorHandler interface (creating SACErrorHandler).
- Use latest SheetErrorHandler changes in CSSDocument implementations.
- Move constants from AbstractCSSRule to ExtendedCSSRule.
- Revert "Add 'public static' to CSSPrimitiveValue2 level 3 unit identifiers."
- Change method signature of a couple of internal keyword-related methods, for 
  consistency.
- Do not report unknown custom rules to SheetErrorHandler.
- Small fix to internal method lexicalUnitToString (used for testing).
- More unit tests.
- Format some unit tests.
- Some javadoc improvements.
- License information update.
- Switch NodeStyleDeclaration license to W3C-20150513.

 * Dom4j module:
- Use latest SheetErrorHandler change in XHTMLDocument.

Version 0.40.1
--------------
 * Core:
- NSAC implementation: discard at-rules with unmatched parentheses.
- NSAC implementation: fix bug in the handling of some column combinator
  selectors.
- CSSOM: change CSSInheritedValue to CSSInheritValue.
- CSSOM: clone expressions / arguments when cloning calc() or function values.
- CSSOM: complete the inheritance infrastructure, absolutizing relative units 
  inside calc() and functions.
- CSSOM: create type identifiers for functions and gradients in 
  CSSPrimitiveValue2. Remove isFunctionValue().
- CSSOM: introduce the CSSExpression and CSSCalcValue interfaces.
- CSSOM: add a CSSGradientValue interface.
- CSSOM: handle 'currentcolor' in computed styles.
- CSSOM: refactor in CSSValue creation.
- Move shorthand setters out of already bloated BaseCSSStyleDeclaration.
- ShorthandSetter: remove a sanity check that could mess the detection of bad 
  values.
- Use fast path constructor instead of parser to create some identifier values.
- Add 'public static' to CSSPrimitiveValue2 level 3 unit identifiers.
- Add a comment and a test about the initial value of 'background-color'.
- Changed a few Javadoc comments.