Entailment graph statistics

[gennadil]

We're working on extracting statistics from the entailment graph.

We need to be able to extract:
• The size of the corpus (the number of documents used to build the graph)
• The number of text fragments in the corpus
• The number of nodes in the corpus

In the demo there are few methods that extract statistics:
• graph.getNumberOfEquivalenceClasses()
• graph.getNumberOfEntailmentUnits()
• graph.getNumberOfTextualInputs()

This is a history issue that was added fordocumentation purposes only. Please discard it (and close it).

[KathrinEichler]

I think this issue relates to the transduction layer, so I suggest to add it there: https://github.com/hltfbk/Excitement-Transduction-Layer