This will do for now to meet popular demand

"Advanced Open File" menu opens a "media" chooser, an "Open Media" named
dialog. Keeping "Open File" is wrong then.
Compared to this menu, Open "File", "Network", "Capture" and "Disc" are
just 'shortcuts': They needed to be grouped then.

This temporarily removes CAM support (which was reportedly broken a few
days ago). Scan is left for the time being.

Use cqam:// as BDA already does.

(there was no guarantee that each graphic item could be safely casted to
epgitem)

EPG entries can have varying start or end time.
More efficient than looking for non-updated items.

- Change data structures to deduplicate data.
Using the right structures, most data is available in dictionaries keys
and items. (epgevent now unused)
- Use signals and slots to manage QMap indexed channels
(widget storage were required for channel list et number)
- Removes EPGEvent memory leak on focus notification

This is done according to oscillator configuration.