Tvheadend

As kind of discussed at https://tvheadend.org/issues/3134 it is not optimal to parse every config file at boot up.
At non SSD/HDD devices it could slow down the start-up enormous (60-100sec). Even at HDD is it a problem if you use WOL or have an OS with fast start-up.

The idea is (maybe someone have a better one) to generate a cached version of the config files with an "cheap" compression (*.xml.gz or *.plain_text.gz) to avoid heavy cpu usage at low end devices (arm).
Instead of loading the easily 1000+ config files at start-up Tvh could read the single file (<1mb) which was cached at the last config file change. (make it optional so everybody is happy)
If this file doesn't exist/broken/0kb simply load the normal ones at second try.

This would work around to not break backward compatibility.
Kind of better would it to store the whole config at a db (sqlite?) -> would break a lot of course (4.3/4.4?).