[backend-slicer] Added fact() support; use cube.basename;  added default model provider
Make sure that cell object exists (despite being empty)
[backend-slicer] Added cell()
[server] Added reusable formatted_response()
Added formatted response to /members; use formatted_response() in /facts
Implemented members() wrapper – calls provide_members()
[backend-slicer] Added provide_members()
Don't forget to advertise it...
[backend-slicer] Fixed cell()
Added default path_details which gives only key and label attributes, rest is set to None. Now any browser can provide dummy cell()
[backend-mongo] Updated members() – use the new interface; added implicit dummy cell
[backend-mixpanel] Added dummy cell support
[backend-sql] Use new members/provide_members interface
Added bunch of logging timing output
Wrap INSERTs in a transaction instead of using autocommit; added debug logging
Added some temporary SQL debug logging
Fixed imports, closes #164
[server] Added JSON line logger
Removed obsolete semi-additive checks
Move the exclude_if_null into the result iterator