Merge branch '517-simple-ui-for-managing-rss-feeds' into 'master'

Simple UI for Managing and Importing RSS Feeds

Please note that this does not yet include the reblogging style for displaying imported RSS entries.

![device-2016-07-26-170732](/uploads/e7f53f72e955d0c37518e0d552121105/device-2016-07-26-170732.png)
![device-2016-07-26-170755](/uploads/b8e0c91ed496b618d330364e840458dc/device-2016-07-26-170755.png)
![device-2016-07-26-171519](/uploads/fae5c16255d5a67673a4bd9be73c165f/device-2016-07-26-171519.png)

Closes #517

See merge request !251