Parsing treebanks

Starts to read in an intial state from treebank templates.
Not very sophisticated right now - also shows some signs of coupling between the treebankRetriever and the morph plugin: The mere presence of a postag is enough to couple them. Needs to be overcome, but we're taking it step by step.

The treebank file itself is a stub right now. We act only on one sentence. A navigational plugin needs to be set in between if we want to move between several sentences - but this has to be decided a little later this week.

The morph plugin saw updates during this as well, it can now handle postags (in both directions, from plain attributes to a postag and vice versa)
The configuration file got loaded up with the Latin morphology set currently used in the Latin Dependency Treebank.

Many open questions - the retriever as well as the morph plugin both act on the assumption that a `morphology` namespace is present in the state object. Has been talked about in #46.
We will soon see if this leads to problems.


A global arethusaUtil object is now present which should help tidying up the javascript code in some places.

Gets us a bit closer to #46.