* 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

* missing various since

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

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

* Missing version

* Updated xwiki.properties file with the new config property

* Documentation in xwiki.properties

* Minor doc improvement

* Typo

* Introduce a configuration to either use the JavaScript compiler or LESS4j

XWIKI-11067: Add ability to catch exception from velocity scripts
XWIKI-11050: Do not fail the UI when there's a problem rendering the document's content
* Document title

- update list of tools installed by default

- Removed the previous implementation, since it was causing problems for tests that must run fully offline

* Revert changes that were not good

XWIKI-10625: Provide easy access to the Mail Sender API configuration from scripts

XWIKI-10623: Mail sending should always work when "from" is not specified and use "admin_email" xproperty instead
* Generate a warning

* Document new configuration property names

XWIKI-10431: In major installations, Filesystem Attachment Store deleteEmptyDirs() can block startup for significant time.
Accidently set the since to 6.0M1, thanks Vincent for catching me on that.

XWIKI-10431: In major installations, Filesystem Attachment Store deleteEmptyDirs() can block startup for significant time.
Add store.fsattach.cleanOnStartup to xwiki.properties

XWIKI-10185: Add a script service to know if path mode is enabled and what is the default alias suffix.

* Fix both.

XWIKI-10185: Add a script service to know if path mode is enabled and what is the default alias suffix.

* Fix both.

XCOMMONS-516: The list of allowed Class methods is way too restrictive in Velocity default configuration
* update documentation

XWIKI-9724: Introduce configuration parameter for the link checker to exclude pages from being checked

XWIKI-9520: Add support for extracting wikis using Wiki Descriptor in passed URLs using the new URL module
* Document new configuration property to decide what action to take when a requested wiki doesn't exist
* Fix @since versions

* Better default configuration that prevents users in corporate environment to have to open another port

* Added configuration

XWIKI-9376: Short URL don't work anymore
* Let the user override the entity path prefix