WIP commit. Changes to integrate the ODIDLiveSimulator into ODIDMediaEngine

Changed MediaEngine.create_data_source_for_resource () to allow an Error
 to be thrown - since we have an additional error path now (but there was
 already one there). Updated librygel-server and simple/gst MEs.

Moved a lot of the code for resolving the item URI to the resource URI from
 the DataSource.preroll() into a utility function called from
 ODIDMediaEngine.create_data_source_for_resource(). This allows the resource
 fields needed to bring up the live sim to be read by the MediaEngine logic.
 The ODIDDataSource now takes the resource URI as a parameter.

Changed the ODIDDataSource.preroll() to always include the
 DLNAAvailableSeekRangeResponse when in live mode. This doesn't seem to be
 disallowed by spec. But this should be an interim solution until we come
 up with a way to communicate a getAvailableSeekRange request to the ME.

Moved resource/content info file utility functions into ODIDUtil.

Added some robustification to the resource.info processing in
 ODIDDataSource.preroll(). It wasn't dealing with blank lines well.

Cleaned up/improved the ODIDDataSource debug logging. It now prefixes
 output lines with the "short" resource name.

Declared all the ODIDUtil functions "internal", made all elements static,
 and removed public factory method.

Verified (pre-start) live resources are being generated properly (S0/SN-
 increasing, LOP bits set, etc)
Tested streaming of non-live resources to ensure no regressions there.