Created the pop-up for groupSuggestion
Added layout of userRow for group suggestion dialog.
Finished the functionality implementation of the pop-up for group suggestion and added necessary API modification.
Fixed the moment when the group suggestion pop up is displayed.
Fix a risk of pop-up pile up
Fixed a couple Checkstyle violation in GroupsActivity
Fixed a bug with group suggestion dialog.

The bug was that the App's state was not consistent anymore if the user dismissed the dialog using the BACK key instead of the Cancel button. Booleans were not updated.
Restored the frequency of refresh of GroupsActivity to 2 minutes (was 10s for testing purposes).
Merge branch 'groupSuggestion' of https://github.com/lca4/unison-android into groupSuggestion
Updated JsonStructs to the ones found on the server.
forgot to add a file in previous commit solving a bug with the popup
Merge branch 'groupSuggestion' of https://github.com/lca4/unison-android into groupSuggestion
Almost finished implementing location management. WARNING code is buggy, we still need to replace Position by Pair<Double,Double> in order to serialize it
Updates tags handling

- The whole process to fetch the top tags from the gs server is updated.
- Corresponding data structures are updated as well
Fixed some Checkstyle violation and added the autoleave functionality to MainActivity. Not tested for now.
Single-user mode

- Makes use of Playlist object
- Introduces context menu for playlists list
- Uses generic layout list.xml
Single-user mode

- Updates database:
  - table "tags" renames to "tag"
  - adds "is_checked" field
- Updates according to changes above
Removed uid from URL in requests for suggestions.
Changes tag seeds selection handling

- introduces is_checked field in tag table

Misc:
- FIX not autoincrementing row id in lib_entry table
Added intervals for location fetching. Added the Set Password in menu when DJ (not the functionality behind).