larger avatar in the "in reply to" box

This one is for @BrentleyJones (cf.
http://meta.discourse.org/t/small-avatar-in-in-reply-to-box/8761)
added the "allow uploaded avatars" site setting
custom avatar support
generate avatars rake task
cleaned up non-used code
updated model annotations
updated locales
updated NGINX sample configuration
Merge pull request #1320 from ZogStriP/local-avatars

Local avatars