Adapted imports and setup.py to changes.

WIP: Cleaning up the structure of Space classes. Tidied up the chain PowerIndices -> PowerIndexFactory -> Space -> PowerSpace; including paradict.

- rename transforms submodule to transformations
- Add a Transformation class which wraps the actual transform class
- Derive and implement RGRGTransformation
- Add tests

Therefore made the Field_type base class more advanced.
Added default field dtype to nifty configuration.

Added first version of field_type classes.

Included version.py for __version__ attribute.
Included new nifty_config and d2o_config files.

Some bugfixes.

Abstracted the power_indices class from rg_space -> Implemented a lm_power_indices class.
In the middle of space-interface cleaning.

Resorted the packages and the import structure.

Refactored get_data/set_data-routines.
Added d2o_librarian.
Started work on updated unittests.

Started rework of the d2o slicing: introduced 0-dimensional advanced indexing capabilities.

-> Many minor and major bugfixes
-> Reworked indexing (now works with negative step sizes, too)

Updated the naming of domain, codomain, target and cotarget in the spaces, fields and operators.
-> The propagator_operator is now 3 times faster

Reworked init of d2o.
Implemented a distributor cache.

Added a mpi_dummy.py. Integrated the paradicts to the spaces. Implemented unary_operation, binary_operation and norm in the spaces. Extended the functions of the distributed_data_object for the unary and binary operations.