Tag for the 3.1.6 release.

Version 3.1.5 changelog:

* Improved rover support.
* Bug fixes.

Version 3.1.4 changelog:

* Fixed performance issue with the google maps provider.
* Cleaned up unused assets directory.
* Add option for enabling/disabling of the imminent ground collision warning.
* Fixed invalid reporting of follow me radius.
* Added support for arming/disarming on plane: To make use of that feature, the `ARMING_REQUIRE` parameter must be enabled (value of `1` or `2`)

Merge branch 'master' of github.com:DroidPlanner/droidplanner into ve…

…rsion_3.1.3

Version 3.1.2 changelog:

* Droneshare account ui cleanup.

Version 3.1.1 changelog:

* Fixed 'undo' crash bugs, and glitches.
* Fixed crash bug caused by changing command mission items to waypoints.
* Fixed invalid toast message when failing to login to Droneshare.

First stable release for 3DR Tower.

Bug fixes.

Tower version 3.0.16 RC

* Added ability to modify the GUIDED SCAN follow mode roi altitude.

Tower version 3.0.15 release candidate:

* Added GUIDED SCAN follow me mode description.