Promoted the clang plugin's _NameFilter to dxr.filters.
Fixed _NameFilter to not freak out if its needle type isn't in the results.
Basic support for Python class and function definitions.
Renamed _NameFilter to NameFilterBase.
PEP8 imports in python/indexers.py.
Removed extraneous makefiles in the Python plugin tests.
Broke out the Python filters into their own module.
Import NameFilterBase from dxr proper, not the clang plugin.
Merge very basic support for Python indexing: functions and types (classes) so far.