Also rename the style module from 'ext.categoryTree.css' to
'ext.categoryTree.styles'.
Keep the previous module name 'ext.categoryTree.css' for compability to
cached versions.
Also move the files of the module 'ext.categoryTree' into a
subdirectory ext.categoryTree.
Change-Id: Ie5ea28acfb43e33a94ec5824baf4f26d63d8e9e6