Some bugfixes.

Many bugfixes and new tests for rg_space.
Fixed imp part of dependency_injector.

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.

Removed trailing whitespaces in nifty_operators.py

-> Many bugfixes and refactorings.

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

Added some ufuncs to point_space, field and distributed_data_object.
Updated the projection_operator.

-> 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.

Implemented interface for slicing methods in slicing distributors. fftw_distributor is now a special case.
Implemented flatten routines for d2o.

Fixed a small error in random number generation in nifty_lm.py

Finished operator and diagonal_operator.

Added direct_dot to nifty_simple_math.py.
Begun with direct probing implementation.