Admin dir separated from default TPL

Admin part is separated from all other templates, cause I dont think
that administrative part will be changing alot (skins and etc), so let
it be in other folder. Also defined new ADMIN_TPL_DIR constant for
proper including.

All admin related files now stored in /tpl/_admin folder.

Minor changes in TPL such as automatic year date, etc.
Removed some hooks to run in admin interface part, cause we don't need
them there.