Created custom number picker preference. Currently not working correctly.
Cleaned up Message/Post time limit options, added NumberPickerPreference to message option.
Fixed numberPickerPref so that the correct preference is stored persistently. Still need to check if default value is working on fresh install.
Merge branch 'feature/difficultSettings' of https://github.com/TAMUSeniorDesignCS/MobileApp-Android into feature/difficultSettings
Added default value of 48 for message forget time setting
Merge branch 'feature/difficultSettings' into develop