build: add default Autobuild job (debian)

This works fine for most native compilations, so saves spec'ing anything else.
epggrab: ensure / in channel ID doesn't cause config failure. Fixes #1774.
epggrab: reduce spam in the logs, fixes #1839.
iptv: ensure startup will not block installation of PID filters
iptv: allow non-multicast IPTV (useful for testing)

I don't actually check for valid MC group address, I simply try and add group
and just warn if it fails (but carry on anyway).
support: updated some random helper scripts
mpegts: ensure that PCR (and PMT) are properly opened by service and recorded.

Fixes #1884.
add option to only allow user to access the tag that matches username