Options to disable channel icons and recordings or fanart images

Lower powered systems like Raspberry Pis have resource issues trying to load all the channel and recording images, icons, and thumbnails. This gives the options under Advanced to disable them.

The change of the options requires a PVR database reset to clear out the cached information from before. There is no trigger in XBMC to force this at this time. It must be done manually.

I was going to add a dialog popup on the settings screen to notify users of this, but I didn't see a precedence set in the plugin on how to do this so I left it out at this time.