updated the usb connection implementation to provide a fallback if the ftdi library fails.
added logging to investigate the ftdi library failures.
Mavlink: Update Mavlink library
added debug and GA logging to monitor the used usb type.
Merge pull request #1042 from ne0fhyk/feature_improve_usb_connection

Feature improve usb connection
add german strings for tts warning preferences
Merge pull request #1045 from squilter/issue_1034_more_german

add german strings for tts warning preferences
Merge pull request #1038 from arthurbenemann/mavlink_update

Update Mavlink library
fixed issue #1043
Merge branch 'master' of https://github.com/DroidPlanner/droidplanner into fix_issue_1043
Merge pull request #1046 from ne0fhyk/fix_issue_1043

Fix issue #1043
Version: Releasing version 2.7.3
Core: Log messages after sending them to the app

The queueToLog() method was consuming the fields of some of the messages and the app was receiving incorrectly parsed messages.

This closes #1050
Merge pull request #1056 from arthurbenemann/issue1050

Core: Log messages after sending them to the app
Core: add extra follow modes back
Core: Removed Wake-board follow-mode
Core: change the way the default follow mode is instantiated
Android: Update the radius label on the follow-fragment when the follow mode is changed
Merge pull request #1057 from arthurbenemann/follow

Core: add extra follow modes back
Version: Releasing version 2.7.4