Help WebUI Fix

First commit working on the help content and integration.
Summary is here :
https://www.icloud.com/iw/#numbers/BAIGS4VMg0uDnLQhOhqBzmIPZ3rb00E48p2F/
TVH_Help

This commit :
- Adds missing Help buttons on UI panes.
- Creates docs files related to those buttons when missing.
- Content will be reviewed later, currently « In progress » is
displayed in new help files.
DVB Help update
epggrab: test code for only tuning muxes that require it
epggrab: fix the missing variable initialization and NULL dereference
epggrab: eit - fix the shutdown sequence
epggrab: fix a memory leak for ota mux
epggrab: improve the tune callback, do tsid check for opentv
epggrab: otamux - save linked services, too
epggrab / eit: add automatic linked service removal
epggrab: ota - move service lists from ota to map

- also use service filter for uk_freesat / viasat_baltic
epggrab: increase default timeout to 600 seconds (10 minutes)
epggrab: ota - remove timeout / interval per module / per ota mux config
cron, internal epggrab: add multi-line cron support for internal epggrab
epggrab: ota - change the subscription scheme

- now all muxes are handled continuously in one queue
- the queue can be kicked using the start time
epggrab: ota - add multi-line cron scheduler

- the initial EPG scan can be turned off in webui
- the OTA mux timeout is configurable through webui
epggrab / mpegts mux: allow to force EPG scan per mux
webui: epggrab - do not collapse panels by default
mpegts mux dvb: remove the migration code (it's in src/config.c)
epggrab: migrate config in src/config.c
Add mpegts_mux_nice_name() function