App should be able to take any scta url (expression, manifestation, transcription)

[stenskjaer]

Suggested by Jeff:
Lbppy should be able to take any scta url -- expression, manifestation, or transcription -- and resolve to the canonical transcription and find a file. So if I give it the url for a specific transcription, lbppy should know this is a transcription and look directly for the location of the file but if it is a url for an expression or manifestation it should call the “canonical_transcription” method proper to each class.

An expression can take many manifestations which can have many transcriptions. So when we give the app the expression address, it defaults to the canonical manifestation and then further defaults to the canonical transcription of that canonical manifestations.