Settings
- implemented a settings menu and activity/fragment for MainActivity
- at the moment, it only contains a single-choise list to set the wanted precision of localisation services

Bottle
- when setting localisation of bottle, the setting is used to trim the double values in latitude and longitude direction

Refactoring
- strings xml, BMail, Bottle, MainActivity, MessageActivity etc.

JSONParser
- thrown out... all functions are obviously related to Bottle and BMail objects, so the JSON functions became part of these classes