FILEMAN-72: Extract the tree code into a generic widget and move it to the XWiki platform
* Describe the drive tree structure in a wiki page (DriveTree).
* Add rights checking for drive tree UI actions (i.e. disable or hide actions that are not allowed for the current user).
* Unpack the tree widget and jobRunner webjars and attach their resources to some wiki pages to be able to used them on older versions of XWiki that don't support webjars (e.g. 5.4.5).