Fix introduction, add new icon to detail map to stop location, bugfixes

Summary:

• Don't show permission button for location on Android 21

• Remove markers from the map when they are assigned a different direction

• Fix new button position

• Add icon to map in LinesDetailFragment to stop using GPS, fix bug in MQTT

Reviewers: valerio.bozzolan

Reviewed By: valerio.bozzolan

Subscribers: valerio.bozzolan, Libre BusTO

Tags: Libre BusTO

Differential Revision: https://gitpull.it/D148