BTConnection: save selected BT connection device until reset by clearing Settings-> Connection Preferences -> Bluetooth Device
formatting
moved preference stuff to DroidPlannerPrefs
Created "forget" button instead of a textedit.
moved dialogs to strings.xml
Merge branch 'master' into bt

Conflicts:
	Android/src/org/droidplanner/android/fragments/SettingsFragment.java
	Android/src/org/droidplanner/android/utils/prefs/DroidPlannerPrefs.java
Merge pull request #879 from squilter/bt

BTConnection: save selected BT connection device