JSON-dump POST data for all requests

The API expect the POST data to be json formatted strings instead of the dict itself.
Make it possible to add a phase to a project

Note that the index doesn't seem to work - even you using
the dev console AgileZen provides.
Use 4 spaces instead of 2 in python files

For multiple reason:
- I usually work with 2 and wanted to try 4
- Landscape doesn't offer the possibility to configure that yet