Purge more dead code.
Minor fixes to xbmc.js

- Be specific when comparing boolean values
- Whitespace
- xbmcJsonRPC converts parameters to JSON string, no need to do it before hand
Clean up and simplify Ext.data.XBMCProxy
Empty genre fix no longer required

XBMC no longer returns a blank genre when getting the genre list, so
this work around is no longer required.
sendJsonRPC handles the encoding of JSON no need to do it before calling.
updateXBMCSet no longer required.

It's now handled with everything else in updateXBMCTables.
Update change log