EIT crawl transport scan

[stuarta]

This modifies the current all channel EIT crawl to a transport crawl, while still visiting all channels.

This is done by getting the channel list with mplexid (aka transport) and building the channel list so that each channel selected is from a different mplex to the previous one.

eg. If your mplex to channel map was as follows

M. ChChCh
1. A B C
2. D E F X Y Z
3. G H I

Your channel list to scan comes out as A D G B E H C F I X Y Z

Thus scanning all channels, but visiting each transport as quickly as possible.

[stuarta]

the patch

[stuarta]

Forgot to mention that inputs that are designated dvb_on_demand will be ignored. This use useful for people with USB tuners that could be removed.

[danielk]

(In [7422]) Closes #437.

I did not add the part where it disables channel scanning entirely if you are using dvb-on-demand. We should instead just sleep for a while between scans. I also added a check for "useonairguide = 1" to the channel query for the scan.