[win32] Enable SSE2 everywhere
removed: BackGroundInfo Loader multithreading (no longer needed)
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
changed: Split background info loading into a 2 stages

This allows us to first perform loading of cached (fast) stuff and after that load the lookup (slow) stuff (partially fixes #14071)
[VideoInfoScanner] If no matching subepisode in guide, try full episode
[configure] fix goldlinker check
Remove extraneous empty-string check (URIUtils::IsInternetStream() and CFile::Exists() both handle empty strings)
Don't show "Add to Favorites" context button for "Get More..." add-on links
changed: Renamed m_database to m_video/m_musicDatabase for clarity
changed: Use a member variable for the texture database

This speeds up thumb loading considerably. This also gets rid of the Initialize/Deinitialize ThumbLoader functions
fixed: Music thumb loading for files view was slow

This was caused by the fact that we never checked for cached images for music items
fixed: Thumb/flag extractions were never stored when used outside the bg infoloader

Also factored out some (obsolote?) code as a bonus
Merge pull request #2890 from arnova/thumb_loader_refactor

Thumb loader refactor