csclient: new package
csclient: minor fixes for review
Merge pull request #145 from rogpeppe/061-csclient-package

csclient: new package

This is the start of the client-side charm store code.

We also factor out the JSON equality checking so that the csclient tests
can use it.
Added search filter functions.

Added support in the elasticsearch DSL for the
filter functions defined in http://tinyurl.com/qzobc69