Replace rc override service with topic

[vooon]

@tonybaltovski requested in #22.

I think topic more suitable for override stream (and FCU does not send ACK), so i decide replace it.

[tonybaltovski]

Thank you. I will test this.

[tonybaltovski]

@vooon This does not actually get used by the FCU. Have you tested it?

[TSC21]

In #133:

Perhaps PX4 don't handle RC override messages, i can't find handler for MAVLINK_MSG_ID_RC_CHANNELS_OVERRIDE message.

In the matter of fact, it isn't supported. You have propose that in the PX4 Firmware issues.

[vooon]

@tonybaltovski I'll test it with APM, they support it, but require mavros system id == SYSID_MYGCS.

https://github.com/diydrones/ardupilot/blob/9de1ae8fbbb4cf614bd59203c7605787241e60b4/ArduPlane/GCS_Mavlink.pde#L1350

[tonybaltovski]

@vooon Does it matter that I am not using a gcs? Also, I tried the teleop with an APM and it was not changing when data is sent. @TSC21 Have you tried this?

[TSC21]

@tonybaltovski check my above comment.

[vooon]

@tonybaltovski try to set gcs sysid:

rosrun mavros mavparam set SYSID_MYGCS 1

Note: APM silently drop override if it comes not from gcs sysid, PX4 don't support this message at all.