Start potables tests
Remove fields not used for main analysis
Adding pytables database in parallel for now
Revert "Remove fields not used for main analysis"

This reverts commit f2a98d6b22ec73345cb34dbca7d84f8387abd6d7.
Clean up comments
Add rates and frequencies to database
Shift everything to pytables / get rid of shelve

This required some major changes inside subsets. Results now get stored
in a numpy record array. More work is needed to benefit from this.
Merge branch 'develop' into feature/pytables
Merge branch 'develop' into feature/pytables
Merge branch 'feature/pytables' into develop