Upgrade to Velocity 2.2

See http://velocity.apache.org/engine/2.1/changes.html

Among the main new features and enhancements:

+ Logging to the SLF4J logging facade.

+ Configurable whitespace gobbling.

+ Method arguments and array subscripts can now be arithmetic expressions.

+ Configurable method arguments conversion handler with automatic conversions between booleans, numbers, strings and enums.

+ Significant reduction of the memory consumption.

+ JSR-223 Scripting Engine implementation.

For notes on upgrading from Velocity 1.x, see http://velocity.apache.org/engine/2.1/upgrading.html.

Things to do with the upgrade:

• look at new ConversionHandler system for parameters conversions. See http://velocity.apache.org/engine/devel/developer-guide.html#method-arguments-conversions
• use Velocity side DeprecatedCheckUberspector
• take a look at http://velocity.apache.org/engine/2.0/developer-guide.html#space-gobbling
  • the default white space handling is different
  • we might want to replace our VelocityMacroFilter (or some of them) by new Velocity gobbing system (Structured space gobbling is the closed to what is the default in wiki velocity macro)

Former blockers now fixed/worked around:

• fixing https://issues.apache.org/jira/browse/VELOCITY-896 fixed in 2.1
• fixing https://issues.apache.org/jira/browse/VELOCITY-897 fixed in 2.1
• fixing https://issues.apache.org/jira/browse/VELOCITY-889 fixed in 2.1
• reverting https://issues.apache.org/jira/browse/VELOCITY-542 retro compatibility option provided in 2.1
• find a workaround for broken #setVariable, might actually be fixed by https://issues.apache.org/jira/browse/VELOCITY-904 retro compatibility option provided in 2.1
• Velocity 2.1 release done
• https://issues.apache.org/jira/browse/VELOCITY-912 fixed in 2.2
• https://issues.apache.org/jira/browse/VELOCITY-923 fixed in 2.2
• https://issues.apache.org/jira/browse/VELOCITY-924 fixed in 2.2

Remaining blockers:

• https://issues.apache.org/jira/browse/VELOCITY-904
• no more implicit Velocity macros local context
• Velocity 2.2 release

Might be a blocker:

• there seems to be a memory leak in org.apache.velocity.util.DuckType keeping classes which may have been reloaded (when upgrading/uninstalling an extension for example), see https://github.com/apache/velocity-engine/pull/6