Configurable vehicle model

configurable vehicle model

I'm missed this when do #407.

Sync with: https://github.com/mavlink/mavlink/commit/1fc4aef08a54130f297943c246f95b8c7e37b1bf

Mavlink package provide information about known dialects,
so we do not touch mavlink_dialect.h selection ifs.

It is not complete, but i hope it helps in current state.

Also fixes: environment variables may contain ~ (user dir) in expansion.

Updated local position subscription topic for setpoint demo

Altitude plugin