epggrab: ensure muxes with no (or disabled) modules aren't started
subscriptions: reverse EPG and initscan priorities

For networks with extended EIT, having EPG take precdence causes chaos
during init scan. The reality is that forcing an EPG scan to stop because
someone wants to scan a new mux is probably the right thing to do anyway.
linuxdvb: allow init scan to be started/stopped by setting initscan state
webui: minor correction to checkbox controls