Add more fields to RSS feed description

Currently, the description for an episode in the RSS feed contains simply the description stored in MythTV. I would like to enhance it to contain more information, such as:

Show title
Episode title
Channel
Recording time
Episode number

for example. Maybe other things could be added, such as the name of the mythexport config file which was used. Or the length of the file, both in megabytes and in time, if that's possible to determine.

Although the show title and episode title are already included in the RSS feed of course, depending on one's podcast player, they can get truncated, so it would be good to add them to the description.

I suggest that this additional info should be added *after* the existing description, so as to not annoy people who expect to see that at the top, or in case their podcast manager shows a snippet of the description when browsing episodes.

This would require changes in mythexport-daemon.