interfaces: add ILanguageInvoker and ScriptInvocationManager
python: implement CPythonInvoker (replacing XBPyThread)
XBPython: cosmetics
python: let XBPython implement ILanguageInvocationHandler
cosmetics: remove trailing spaces from XBPython.h/cpp
python: register XBPython for .py files
use CScriptInvocationManager instead of XBPython
[win32] update VS project files