Feature: Allow mangement of <role>s via admin/ interface.

This allows to manage <role>s via admin interface if the role supports.
Also format of admin/manageauth has been changed:
- <source> was renamed to <role>.
- mount parameter was removed.
- <role> got new parameters: type, name,
  can-adduser, can-deleteuser, can-listuser.
- can-* parameters are bools ("true" or "false"). They should be used
  to show or hide elements on the admin interface.

Ticket #2123 is nearly complet with this, just admin/manageauth.xsl
needs up be updated. Please close the bug in the commit that updates
admin/manageauth.xsl.
See #2123