[region,data] added tests for masking of region; deactivated support for KDTree in plotting as this caused some trouble with cpython code compilation. The KDTree option is supposed not to be used anymore anyway
[bugfix] fixed cython import problem. CYTHON routines are not not compiled any more on the fly, but have to be compiled ONCE when checking out the code. This is done by running the setup_extensions.py script (see documentation there)