v0.20.0

Features:

• Add geofence to mavsdk_server (#856).
• Add MAVLink FTP plugin (#774).

Bugfixes:

• Fix target system ID check (#862).

Improvements:

• Remove unneded version define in cmake (#867).
• Move to jsoncpp and make non-superbuild work with jsoncpp and tinyxml2 (#865).
• Small improvements to telemetry plugin and test (#863).
• Only sleep if required in integration tests (#859).
• Remove caching in params (#847).

Contributors:

@coderkalyan, @irsdkv, @julianoes, @MatejFranceskin