* Added various UI to change values for misc accessibility prefs.

TODO: add the backend part in XWikiUsersDocumentInitializer.java L104 and the actual useful part in stylesheets.vm L54

* Removed unused accessibility options from the prototype

* Added the parameter logic

* Tried out updating the less skin variables, still unfinished

* Added various UI to change values for misc accessibility prefs.

TODO: add the backend part in XWikiUsersDocumentInitializer.java L104 and the actual useful part in stylesheets.vm L54

* Removed unused accessibility options from the prototype

* Added the parameter logic

* Tried out updating the less skin variables, still unfinished

* Removed the tentative for personnalized LESS parameters - font size here

* Added back the preference for text size (flawed implementation like what it used to be)
* Fixed the place where we loaded the CSS

* Cleaning up PR

* Updated translations
* Removed a useless improt from stylesheets.vm
* Changed option order

* Fixed codestyle

Co-authored-by: Michael Hamann <[email protected]>

* Fixed codestyle

Co-authored-by: Michael Hamann <[email protected]>

* Added translations for the field values

* Updated the title level

* Removed the reference to the flamingo skin

* Changed the cache policy on the user preference file

* Updated the selector

* Added backwards compatibility: if the old parameter is set to 'accessible' on the profile, it will set the old preferences

* Updated the selector to behave more consistently.

* Added underline and font size options to the XWiki and Space preferences.

* Removed the reliance on wiki defined font-size to prefer user defined font-size

This reverts commit 7bf473e.

* Removed the SSX
* Added style directly in general.less
* Added logic related to preferences in the template htmlheader.vm

* Added an unsetter for the accessibility parameter, and defaults for the new parameters that would get changed if the accessibility parameter is already set.
* Used `@font-size-base` instead of the user preferences as the basis for body fonts.

* Removed changes related to font-size from the PR

* Removed leftover translations

* Deprecated a translation key instead of completely removing it.

* Fixed the preference conditions for underlining preferences