Fix for issue 3064, create skin admin role

- new skins_admin role created
- admin_skins_controller deleted and actions merged into skins_controller
- views moved from views/admin/skins to views/skins and renamed
- new cukes added, but set as pending until the new role can be added to the test database
- I should have probably kept a list of the changes I made as I was making them because I'm drawing a blank now
- added checks for skin admin-ness to user.rb and skin.rb
- other stuff possibly...