Windows GUI: Fix shell extension registries

[cjee21]

Fix bugs to prevent issues such as the following:
https://sourceforge.net/p/mediainfo/support-requests/51/
https://sourceforge.net/p/mediainfo/bugs/1161/

Make sure that associations other than for file extensions in MediaInfo's list are properly removed and no longer added.
Also refresh File Explorer's context menu after install/uninstall so changes are visible immediately.

Tests results:

• Context menu entry appears immediately and for both files and folders after install without requiring MediaInfo to be launched first regardless of MediaInfo's existing settings.
• When MediaInfo is launched, context menu is updated according to settings set.
• If shell extension is disabled, context menu entry no longer shows for files associated with audio/video such as .mp3.
• After uninstall, the registry was searched and it was found that some MediaInfo entries still remain. This should be retested after Update file extensions lists #967 is merged.

[JeromeMartinez]

Context menu entry appears immediately and for both files and folders after install without requiring MediaInfo to be launched first regardless of MediaInfo's existing settings.

I didn't think to when user disabled it then install an update :(.
A nice to have in the NSI would be a test on the registry key, if it exist and 0, no extension installation/update (so install only at the first install)

If shell extension is disabled, context menu entry no longer shows for files associated with audio/video such as .mp3.

Thank you.

After uninstall, the registry was searched and it was found that some MediaInfo entries still remain. This should be retested after #967 is merged.

Please rebase.

[JeromeMartinez]

Just need to rebase.