Updated Visual Studio projects.

1. Added Win32 Bridge Include path to the Win32 Proxy, for sharing of
the Proxy types header.
2. Minor filter fix.
Updated Win32 Bridge to use CSteamIDs.

1. Part of ongoing to switch to only use CSteamIDs instead of uint64s.
This breaks the Linux Bridge, and the Proxy update isn't committed
either.
2. Also, all Win32 code now shares type information.
Updated Proxy to recent API changes.

1. Now properly includes the Bridge headers.
2. User API calls now properly use CSteamID.