added data dumper util in order to debug globaleaks data structures
Upgrade requirement `cryptography` to 0.5.
Merge branch 'feature/fields_refactor' of github.com:globaleaks/GLBackend into feature/field_refactor
Merge branch 'feature/fields_refactor' of github.com:globaleaks/GLBackend into feature/field_refactor
Review and integrate one-to-many relationship between fields and fieldgroups.

To each field correspond a single fieldgroup, and fieldgroups might be collected
in other fieldgroups.
Merge remote-tracking branch 'origin/feature/fields_refactor' into feature/field_refactor

Conflicts:
	globaleaks/models.py
	globaleaks/tests/test_models.py
Fixing fields and fieldgroup relations and writing tests.
Merge remote-tracking branch 'origin/feature/field_refactor' into feature/fields_refactor