* also add a missing older parameter

* Rename "useLegacyParentChildMechanism" to "hierarchyMode".
* Stop pretending parent child mechanism is deprecated. Is is just off by default.

* This commit introduces:
** a "core.useLegacyParentChildMechanism" property to use or not the hierarchy based on legacy parent/child relationship
** a "parentchild" script service to get the legacy parents of a document and to get if the legacy mechanism is used or not
** the support of both modes in flamingo
** use the home icon for the Main space
* This first version does not hide some parts of the breadcrumb if it is too long
* This commits does not fix the failing functional tests

* Forgot some places

* missing various since

* Non working implementation since it's currently not possible to make it work as the web.xml mappins are done for the "standard" URL Scheme + the fact that the Error Handler is also currently hardcoded to use the "standard" URL Scheme (needs to be replaced by a Servlet).
* Even though it's not working, it's still useful to have it committed since it allows us to make sure the interfaces allow to contribute new schemes.
* Big refactoring to make it easier/possible to contribute new URL Schemes.

* Added missing dependency in Package Mojo so that it's available for all functional tests (ie it's in the base flavor)

This reverts commit 43164775.

- Disabled the feature by default and marked it as experimental until the performance problems are fixed.

XWIKI-11843: Watchlist App Email Notification generates incorrect links when XWiki is deployed as ROOT

* Remove the LESS configuration property which is eventually not used.

* The ImportMojo should use the default Admin user to install extensions (otherwise we see "Installed by Unknown User").

* Use the diamond operator for Java 7.

XWIKI-11858: Upgrade Hibernate and DBCP Connection Provider code to work with DBCP 2.1