epggrab: ota - requeue skipped muxes (network check)

- enhance trace
- do not print delete problem? messages on shutdown
epggrab: ota - optimize the eit/opentv workflow

Assume that the EPG grab is completed when:

- no EIT data are present and opentv completed
- EIT data are present but opentv data were not seen
epggrab: ota - improve save caching and add no data timeout

- fix the complete flag load
- improve the save request caching
- mark as completed all timeout states (no data, EPG timeout)
webui: Stream directly for TVHeadend/ http client, too
webui: remove dead code (tvhlog_level)
webui: enable file logging when the log file is set through GUI