Simplify PostCreator - Introduce TopicCreator

Extract code to smaller methods
fix image uploads on s3/imgur
Add 'login required' site setting
Redirect all controllers to login if required

We want to skip the filter for sessions controller so that we can login
and we want to skip the filter for static pages because those should be
visible to visitors.
Redirect to root after login if no path provided

If we do not do this, then people that login from /login will just be
redirected back to the login page. We'd rather have them see the root
path.
Show login modal on header buttons if required
Redirect Ember routes to login if login required
correct message bus regression
implement automatically updating dates in list
Merge pull request #956 from ZogStriP/fix-image-upload-to-s3

fix image uploads on s3/imgur
Started spanish translation
allow onecase switch
Merge pull request #955 from novemberkilo/master

Reduce complexity of PostCreator
Merge pull request #957 from chrishunt/chrishunt/lock-down-the-base

Add 'login required' site setting
es translation is bust, rename for now
missing skip filter for omniauth