Provide plaintext transcription for each Blue Mountain constituent, for Collex indexing

[cwulfman]

Collex includes in its set of RDF triples a predicate, collex:text, that can be used either to include plain text directly in the RDF file or to point to a resource that delivers it (see Submitting RDF on the Collex wiki).

Blue Mountain Springs provides such a resource:

springs/constituent/{issueid}/{constituentid}

So, once the service is up and running, we can supplement our RDF with statements like this:

<collex:text rdf:resource="http://bluemountain.princeton.edu/springs/constituent/bmtnaap_1921-11_01/c003"/>