[mythtv] mythtv master MythNetvision plugin

[Mike Bibbings]

The MythNetvision plugin is no longer building.

local build using ./configure fails on Ubuntu 18.04 LTS:
MythNetvision requires the Python URL library 2 (urllib2)
Disabling MythNetvision due to missing dependencies.

local build using ./configure fails on Raspbian Buster:
MythNetvision requires the Python pycurl library (pycurl)
MythNetvision requires the Python URL library 2 (urllib2)
Disabling MythNetvision due to missing dependencies.

Atleast one buildbot e.g. mythtv master Ubuntu 18.04 LTS disables 
mythNetvision:

https://code.mythtv.org/buildbot/#/builders/22/builds/386

MythNetvision requires the Python pycurl library (pycurl)
MythNetvision requires the Python URL library 2 (urllib2)
Disabling MythNetvision due to missing dependencies.

buildbot for master Debian Buster is also disabling mythNetvision but 
for different reasons.

https://code.mythtv.org/buildbot/#/builders/105/builds/428

MythNetvision requires the Python OAuth library (oauth)
Disabling MythNetvision due to missing dependencies.
Disabling MythZMServer. Requires mysql/mysql.h header

Mike