Re-implement Podcast plugin

- make OPMLBased
- add custom XML browser
- add support for progress tracking: allow user to continue where he
left
Re-implement Podcast plugin

- pause progress reporting when playback is paused
- format time strings
Allow drilling down feeds
Re-implement Podcast plugin

Tweak custom podcast parser to fix ip3k browsing.
Re-implement Podcast plugin

Remove default streams - none of them was working any more.
Initialize settings module if web is enabled.
Re-implement Podcast plugin

The Podcast plugin is not being used on mysb.com. Remove some more code.
Re-implement Podcast plugin

Link to podcast stream managed on mysb.com.
Merge branch 'public/feature/podcast-v2' into public/7.8

Change-Id: I99e28a75aafa0134efcabfd9a6dc63930b390736
Bug 18036: LMS is leaking memory due to disconnected clients

When long-polling Cometd clients disconnect unexpectedly (eg. mobile app
being killed by the OS, or suspended), the client object would continue
to queue up notification events. Kill long-polling clients after 3mins
of inactivity.
Changelog update
Merge branch 'public/7.7' into public/7.8
Allow stopping a random mix from the player or mobile app.
Add a note about the getexternalvolumeinfo notification in the CLI
documentation.
Some RandomPlay cleanup

- remove unused code and variables
- use $client->pluginData or cache instead of global variables
- simplify variable initialization
- silence a DB warnings
- streamline genre handling: don't re-read from the DB over and over again
- remove references to defunct lastplayed check
- register RandomPlay alarms the standard way
- make year mixes behave the same way as tracks - don't queue up all
tracks at once, respect genre filtering
- don't keep the potentially large idList in memory, but in the cache.
Only read when needed.

Fix bug 7823
Don't load ImageBrowser plugin on SN or Touch
Add progress information to podcast listings; fix compatibility with
ip3k player menus.
Podcast settings: allow re-ordering podcasts using d'n'd
Fix adding new podcast
Initialized Podcast feed list preference
Add import from mysb.com feature.