v1.12-beta

# Add
- Improve Overpass and OSM features support
- Add altitude graph to node selector view
- Add altitude graph and seek bar to NodeDetailActivity
- Introducing tool tips in preferences
- MapsForge v0.9.0

# Fix
- Use "sdcard/aat_data" as default directory if possible
- Add notification channel support (Fix crash on SDK 26 devices)
- Use system time to calculate time of life of GPS fix / provide preference to synchronize GPS time with system time. This probably fixes #18

