Add Cql builder for building queries easier

[ilongin]

Hi :)

I have made simple cql-builder that allows me to build queries without concatenating bunch of strings specially if I want to create query dynamically. It doesn't yet support all features of cql but I think that supports mostly for now. So If you think that this might be useful you are free to merge it to original repo. If you have any questions/comments/suggestions about code please tell. I have added unit tests that will make refactoring easier in future if needed.

Ivan