XWIKI-13766: When uninstalling a XAR pages which are part of several extensions are sometimes selected
XWIKI-13764: XAR extension pages index is not properly filled at init

[Misc] Apply new best practice for@since tags (see http://dev.xwiki.org/xwiki/bin/view/Community/JavaCodeStyle#HUseone40sinceperversion )

XWIKI-13704: Remove lock in the XWikiCacheStore
XWIKI-13632: Wrong key generation in XWikiCacheStore

XWIKI-13338: Add ability to override the character symbols used to represent an Entity Reference as a string
* Fix more tests

XWIKI-13338: Add ability to override the character symbols used to represent an Entity Reference as a string
* Fix some use cases using RelativeStringEntityReferenceResolver as a POJO instead of a component (we'll need to fix this to allow overiding DefaultScheme)

XWIKI-13338: Add ability to override the character symbols used to represent an Entity Reference as a string
* Fix some use cases using LocalStringEntityReferenceSerializer as a POJO instead of a component (we'll need to fix this to allow overiding DefaultScheme)

XWIKI-13338: Add ability to override the character symbols used to represent an Entity Reference as a string
* Fix some use cases using DefaultStringEntityReferenceSerializer as a POJO instead of a component (we'll need to fix this to allow overiding DefaultScheme)
* Added some classes forgotten in the previous commit

XWIKI-13338: Add ability to override the character symbols used to represent an Entity Reference as a string

[Misc] Move test to Mockito. BTW I don't understand why the test is using a resolver instead of creating references directly...

XWIKI-13292: Provide a test module to use as dependency for the module manipulating oldcore test tools

Revert "[Misc] Don't have a non-component extend a component (since that makes it inherit the @Component and other annotations). It's also dangerous since the component being extended could add @Inject."

This reverts commit f6c8448c.

[Misc] Don't have a non-component extend a component (since that makes it inherit the @Component and other annotations). It's also dangerous since the component being extended could add @Inject.

- Added protected method for subclasses to override, should they need to.