Commiting Intelledger changes

Aaron, fixed your review comments and updated the pull request with new commit.
Rename this to just ```contains```, and change ```domain.entries``` to ```domain.activeEntries```.

I want the perspective of these methods to be that the normal ones (```get```, ```set```, ```delete```) work on the assumed active entries, and thus other methods will be made to work on **all** entries.