Add TCP Connection to DGPS

[jmachuca77]

Emlid Reach GPS can only publish the RTCM corrections using TCP or Serial connections. This adds the ability to select between UDP and TCP and allows configuration of the IP, PORT, CONNTYPE. It adds four commands (following the ntrip modules model):
start
stop
status
set

by default it is configure the same as it was before (UDP, 127.0.0.1, 13320)

I don't have a GPS that publishes corrections via UDP to test, but it should work. I did test the TCP connection

based on:
https://github.com/antonvh/MAVProxy/tree/reach_inject
by @antonvh

[tridge]

given you are now parsing the data, maybe add status like for ntrip module where it shows counts of each pkt type?

[tridge]

I don't think we want a timer here, instead use the idle task to check for a pending connection. See the start_pending code in the mavproxy_ntrip module

[tridge]

comment doesn't match code, and why read one byte at a time?

[jmachuca77]

I am copying what is done in the NTRIP library:

MAVProxy/MAVProxy/modules/lib/ntrip.py

Line 174 in 041dda2

data = self.socket.recv(1)

[jmachuca77]

This is because the function

MAVProxy/MAVProxy/modules/lib/rtcm3.py

Line 60 in 041dda2

def read(self, byte):

takes one byte at a time.

[jmachuca77]

I have already added the status count for each packet, So that can be seen with the status command.

[jmachuca77]

@tridge This seems to be working pretty good now, let me know if you want me to squash the three commits into one, but I think its ready to merge.

[jmachuca77]

Squashed

[tridge]

please test with both py2 and py3

[amilcarlucas]

This needs a rebase and some more testing.
Part of the functionality is a duplicate from #408. I will close #408 in favor of this one if this ones gets more testing

[stw2nf]

do you have a build that I could test/run? Really interested in this feature. we have a Emlid Reach M2 we would like to automate RTK corrections with via Rpi, but having troubles rebasing this branch on master and actually testing functionality