Create convenience function or class to encapsulate quotation denormalization

[Enkidu93]

At the moment, the burden is on Serval and SILNLP to run the sub-steps necessary to denormalize quotes. It would be cleaner if this were all done within machine. See here for context.

[Enkidu93]

@benjaminking, if you're already doing something like this for your silnlp implementation, feel free to just throw it in machine.py or point to the code in silnlp in this issue. The Serval implementation is here