Mock implementation of a Link

Handy for testing without a real board

Delete Settings from preferences

Offboard mode

Disregard RC_CHANNELS_RAW for signals

This removes double emit of signals.

FlightGear HIL protocol fixes

Update qgroundcontrol.qrc

corrented file name

LinkInterface::bytesAvailable api removal

Put back CRC check

This api doesn’t make any sense given the fact that LinkInterface
signals bytesReceived with the bytes in the signal. Also the reason why
it is never called!

Convert Firmware Upgrade code back to qextserialport

More work on versioning

QSerialPort buffering too slow on Windows.

Settings versioning is handled at the uppermost level with a version
stamp.

Settings versioned independently from app version

Remove OpenSLL pre-req from readme

Remove SSL usage from code