Semi-Final arrangement of some core structural classes for the project.

Let me know what you think. Mike and I worked out this as a good core structure.
I don't know that this interface is necessary/possible without complicating our lives.

I had originally planned for a `DataFilter` class where you could set the field to filter on, the comparison operation, and optionally the type of item (as elastic search sometimes places the type of the object in the url -- this could make parsing all of the filters from a collection of `IItemFilter`s less than enjoyable.)

Lastly, if there are multiple filters we would have to have another class somewhere that knew how to properly conjoin all of the filters such that it could be sent to elastic search.