Add new colortheme variables for the gradients introduced by 3.4 and allow their modification from the colorthemes wizard

XE-1122: Add new colortheme variables for the gradients introduced by 3.4 and allow their modification from the colorthemes wizard - Separated the menu variables into menu* variables (that correspond to the global menu) and menuContent* variables (that correspond to the content menu). Kept the panel - Added the following variables to ColorThemeClass $theme.fieldGradientColor $theme.buttonPrimaryGradientColor $theme.buttonSecondaryGradientColor $theme.panelHeaderGradientColor $theme.panelCollapsedGradientColor $theme.menuGradientColor $theme.menuContentBackgroundColor $theme.menuContentLinkColor $theme.menuContentGradientColor $theme.submenuContentBackgroundColor - Added 2 new configurable areas in ColorThemeWizard: #contentmenu (for elements related to the Content Menu: background, gradient, links) and #extratabs (moved menuSelectedEntryLinkColor here to be closed to the affected area) - Allow the new gradient variables to be modified from the ColorThemeWizard (but the gradient change is visible just in the view mode now, is not real time) - Modified ColorThemeTemplate, DefaultColorTheme, Ruby, Mint and Dusk ColorThemes to be aligned with the variables changes (cherry picked from commit 44379ffd6c098eda2b5fd3b4c3b96bb4764420f0)

XE-1122: Add new colortheme variables for the gradients introduced by 3.4 and allow their modification from the colorthemes wizard - Separated the menu variables into menu* variables (that correspond to the global menu) and menuContent* variables (that correspond to the content menu). Kept the panel - Added the following variables to ColorThemeClass $theme.fieldGradientColor $theme.buttonPrimaryGradientColor $theme.buttonSecondaryGradientColor $theme.panelHeaderGradientColor $theme.panelCollapsedGradientColor $theme.menuGradientColor $theme.menuContentBackgroundColor $theme.menuContentLinkColor $theme.menuContentGradientColor $theme.submenuContentBackgroundColor - Added 2 new configurable areas in ColorThemeWizard: #contentmenu (for elements related to the Content Menu: background, gradient, links) and #extratabs (moved menuSelectedEntryLinkColor here to be closed to the affected area) - Allow the new gradient variables to be modified from the ColorThemeWizard (but the gradient change is visible just in the view mode now, is not real time) - Modified ColorThemeTemplate, DefaultColorTheme, Ruby, Mint and Dusk ColorThemes to be aligned with the variables changes

Merge branch 'XE-1122' of https://github.com/evalica/xwiki-enterprise

XE-1122: Add new colortheme variables for the gradients introduced by 3.4 and allow their modification from the colorthemes wizard - fix ColorThemeWizard values for old colorthemes (color pickers + #content maquette element): -- no value if it's a Gradient variable; -- 'menuLinkColor' for 'menuContentLinkColor' -- 'menuBackgroundColor' for 'menuContentBackgroundColor' and 'submenuContentBackgroundColor'

XE-1122: Add new colortheme variables for the gradients introduced by 3.4 and allow their modification from the colorthemes wizard - fix ColorThemeWizard values for old colorthemes (color pickers + #content maquette element): -- no value if it's a Gradient variable; -- 'menuLinkColor' for 'menuContentLinkColor' -- 'menuBackgroundColor' for 'menuContentBackgroundColor' and 'submenuContentBackgroundColor' (cherry picked from commit 0dfdfa5e597637437d70d9973f7e1488c4fb5c69)