Named graphs

[yfaria]

This PR addresses #24 by changing the code structure. The code consists on populating an IOMemory by creating triples about the structure in the default graph and triples of the items of structure in its specific graph; the profile, item and results of a profile are being encoded on the RDF as well now. The default graph in the CLI is a blank node, where we have the triples of declaring types of the profile URI, each item, the results and each instance of semantic representation and connects those nodes. In the default graph, we still connect the semantic representation URI to its elements (for example, we have MRSs connected to its EPs by the property hasEP). Inside the graph of an instance of a semantic representation, we have the triples between its components and specifications of them; the only exceptions being the INDEX and TOP of structures, in this case the program links a blank node to the TOP/INDEX with the property hasTop/hasIndex in order not to instantiate the URI of the graph as a node. It changed the default format to nquads for expliciting the support of named graphs, but it still supports formats that don't encode it like ntriples or turtle.

About the URI naming problem of #21, the URIs of a profile is the prefix given by the user; the URI of a specific item is {prefix}/{item_id}; of a result is {prefix}/{item_id}/{result_id} and of the semantic representation associated with the result is {prefix}/{item_id}/{result_id}/{sem-rep}; the elements of it are preceded by a hash.
For example, the profile URI would be http://ibm.com/sick/b; the item 33 would be http://ibm.com/sick/b/33; the result 4 would be http://ibm.com/sick/b/33/4; its dmrs would be http://ibm.com/sick/b/33/4/dmrs and the node 10012 would be http://ibm.com/sick/b/33/4/dmrs#node-10012.

After #17, a new logging level was created called SURFINFO for the first level of verbosity and explicitly changing the logging levels depending on the verbosity; it wasn't possible before because the convention was that the first level of verbosity prints messages of level with numeric vale greater or equal of 30, which is the level of WARNING (levels can be found here) . It was done in ba05cde