Revert "Category's for Lists - Part 1." Nice feature but needs perhaps some more work

This reverts commit c7f4b93d8ab18d2f91d3b8cf0fa0cb781f60aae2.

Conflicts:
	administrator/components/com_fabrik/language/en-GB/en-GB.com_fabrik.ini
	administrator/components/com_fabrik/models/fabmodellist.php
	administrator/components/com_fabrik/models/forms/list.xml
	administrator/components/com_fabrik/models/lists.php