* Documentation in xwiki.properties

* Don't fail to get the configured port even when Mail.MailConfig doesn't exist.

XWIKI-11408: Menu Application: Improve default look to make it better-looking with the Flamingo skin

- Because of the bug https://github.com/less/less.js/issues/1968 and after the commit https://github.com/xwiki/xwiki-platform/commit/e9b2bfc9b0b459edfbe79e3abcbfab8367368c2f , we cannot use :extend anymore
- Since I couldn't transform all the extends into mixins (failed for examples like '.dropdown-menu>li>a:hover', etc.) I copied the styling properties from Bootstrap
- In the future, if we fix the extend bug, we should clean this code (either of the properties or the extend comments)

* Fix functional test

XWIKI-11562: Add ability to contribute new Admin categories through ConfigurableClass xobjects
* Fix some bugs

* Fix comment.

* Add @since comment.

* Implemented a workaround because there is a bug in the LESS compiler with @import feature with the "reference" option.
* Delete all temp files properly.

XWIKI-11570: Add getCurrentWikiDescriptor() method to the wiki API to be consistent with the existing getCurrentWikiId() method
- Added missing test to ensure previous coverage.

- Added tests to preserve previous coverage.

XWIKI-10942: The longer names of apps on the Application left panel are not completly displayed on a resized screen

XWIKI-11570: Add getCurrentWikiDescriptor() method to the wiki API to be consistent with the existing getCurrentWikiId() method
- Added both component and script service API methods.

XWIKI-11408: Menu Application: Improve default look to make it better-looking with the Flamingo skin

- Preserved the old styling, but manually prefixed it with .skin-colibri, since Colibri skin doesn't support LESS
- Added styling for Flamingo based skins, making sure they are responsive

* Minor fix (bad merge)

* Use the core.force_text configuration parameter of JSTree to handle node labels as plain text.

* Also select the tree node by default when calling openTo().

* Bug fix to use color theme variables in SSX.

* Put back the email section that should not have been removed from this commit

XWIKI-11540: Adjust the boxes' sizes for mobile

* Fix the build.

* Merge branch 'feature-less-ssx'.

* Because of a bug on the CLIRR plugin, set the CLIRR configuration in the LESS module pom instead of the top level project.

* Minor changes.

* Minor improvement about the cached compiler mutex.

* Close the picker when the user presses 'escape' and so fix the failing integration test.