Added ability to force lowercase tags everywhere.
Added tag search in admin.
Added ability to force lowercase tags and to to prevent a set of "stopwords" via settings. See readme.
Oops, the stopwords feature wasn't working in all cases. Fixed.
force lowercase tags when using manager

Signed-off-by: Flavio Curella <flavio.curella@gmail.com>
Added management commands for merging and lowercasing tags