dvb: forgot to pass netname to sat mux_create
SNR support for all TBS tuners

Drivers fot TBS tuner support SNR
this change work for all models ;)
dvb: re-instate some of the form scanning code.

Mux TSID and ONID can now be updated from other tables if, and only if,
they values are not yet set. Values from the NIT will ALWAYS override
existing values, as they're hopefully more reliable.
dvb: close dvr device on each re-tune
dvr: don't run postproc script unless there is actually a file to process
docs: updated the README and add markdown
Merge remote-tracking branch 'origin/pr/240'
docs: reinstate original README
dvb: add adapter bandwidth to status page.
Revert "dvb: close dvr device on each re-tune"

This reverts commit 03e9f1179d67bd2b4ccd7a0f3fd9c5fc039c0d5c.
cwc: remove duplicate lock causing deadlock on cwc entry delete
tableeditor: ensure all reload operations are properly processed
timeshift: improve rdwr locking to try and reduce stutters.
timeshift: increase play out buffer to reduce stutter due to disk IO.
docs: update documentation about icon caching.
Correct some mistkaes picked up by static analysis.

Thanks to seo for pointing these out.
dvb: ensure that we only create radio/tv services from SDT
dvr: remove bad LIST_REMOVE() call if entry has no channel
Fix #1588 - epg: forgot to check string bounds for epggrab channel name
Fix #1589 - only remove "unsafe" characters if configured to do so.