Improve displaying of the default subreddits

[lucashoeft]

The "Default Feeds" are currently unordered and formatting doesn't look good. The default subreddits should be in an alphabetical order and formatted like /r/AskReddit instead of /r/AskReddit/.

Screenshots

[kgellci]

This would be great! To make alphabetical, I think we need to update the paging for this area to fetch them all at once. Should not be too hard, just some API changes I need to make to expose it.

Formatting of the strings should also be pretty simple. Can create a ViewModel which stores the clean formatted results for display.