Initial Python3 Compatibility

I have updated the cv2 module code and header generator for preliminary support of the various new APIs in Python 3.X.

With these changes, the module will now build and run when compiled against python 3 headers + libs.

I say preliminary because CMake itself appears to have some issues with finding Python3 using FindPythonInterp/Libs, but they don't appear to be working on fixing it. You need to manually specify the python 3 headers and libs when running cmake.

Compatibility:
* Removal of ```dict.has_key()``` calls breaks python < 2.3 compatibility, hopefully that won't be a problem.
* Using ```from __future__ import print_function``` breaks python < 2.6 compatibility and I understand if this is a problem (though py25 is quite old now).