PushNetworkException for network errors on external downloads.

Closes #2112
Fixes #1264

// FREEBIE
Minor cleanup.

// FREEBIE
Move directory refresh from a service over to a job.

// FREEBIE
Move JobManager to external project and dependency.

// FREEBIE
Display 'me' for device's local number in group membership list.

// FREEBIE

Fixes #1494
Closes #1505
refactor preferences into multiple PreferenceFragments
change textcolors
make "enter key sends" dependent on "enable enter key"
improve push registration behaviour
staying in preferences after enabling passphrase protection
invert the passphrase setting
"Incoming" with a capital I
load MmsPreferencesFragment without an Activity, add Summary
improve MMS settings strings