Performance & Clean data

This release adds a new table to take care of the statistics of the projects, making it much faster (specially after a cold boot).

Also, the CSV exporter now generates 2 files, one with the PYBOSSA object data and one with only the info key/values flattened to a 2Dimensional file like CSV. This basically means that you will get a perfect clean CSV of tasks, task_runs and results. As simple as that :-)

Enjoy!