Merge Serveral New Features from Branch

Bugfixes: 
https://github.com/OpenSeaMap/depth/issues/74
Performance Improvements: https://github.com/OpenSeaMap/depth/issues/20

Features:
Introduce Gauges : https://github.com/OpenSeaMap/depth/issues/21
Dynamic License Attribution: https://github.com/OpenSeaMap/depth/issues/16
User Data shown
Track Viewer enables viewing 10m and 100m color schemes