Inconsistent tcp responses

[miklosduma]

At the moment the responses Bluesky sends over tcp are not consistent, and so it can be very difficult to handle these.

• Some commands do not send back anything (DEST, MCRE)
• In some cases wrong commands do not send back a clear indication of them being error messages (e.g. POS command)

It would be useful to get back either:

• {ok, [message]}
• {error, [message]}
message being optional in some cases

Command	Success	Error	Expected
CRE	ok	"CRE acid,type,lat,lon,hdg,alt,spd\n" or "Syntax error: \nCRE: FOO already exists."	ok/(error, Message)
DEST	no response	"DEST acid, latlon/airport\n" or Syntax error: \nDEST: DEST: Position BAR32 not found."	ok/(error, Message)
ADDWPT	ok	"ADDWPT acid, (wpname/lat,lon/FLYBY/FLYOVER/ TAKEOFF,APT/RWY),[alt,spd,afterwp]\n" or "Syntax error: \nADDWPT: Waypoint EGKK3 not found."	ok/(error, Message)
ALT	no response	"ALT acid, alt, [vspd]\n"	ok/(error, Message)