removed t and f 's from group model

removed t and f 's from user model as mentioned in #919
removed t and f 's from group model

removed t and f 's from user model as mentioned in #919

removed t's and f's from category model
merged postgres improvements
keep French localization up to date

:fr:
remove hardcoded value and replace with SiteSetting.cas_domainname
refactored and tested AvatarLookup

less array copying

Avoid N queries
Keep German translations in sync.
Merge pull request #925 from netzpirat/update-german-translations

Keep German translations in sync.
Support incomplete topic urls like /t/just-a-slug; fix error when using route /t/:topic_id/:post_number
Don't allow category slugs that are numbers
Don't append the base url to absolute image urls without protocol.
Extract InviteRedeemer from Invite
Move logic to reject slugs that are just numbers into the slug module
Refactored two class methods into scopes (to achieve a better 'rails way')
Also added some tests to the methods
Merge remote-tracking branch 'upstream/master'
Only pass searchContext type, id in search request
Merge pull request #929 from chrishunt/chrishunt/fix-category-search

Only pass search context type and id in search request
For 403 errors, show the same html page as 404
fix wonky logic figuring out host name
Revert "fix wonky logic figuring out host name"

This reverts commit 114fcb473459dfa4ce262ad2ee99646e4ec2a779.