project: Update gitignore for VS2015 experimental database files.
project: Update gitignore for VS2015 experimental database files.

mwgoldsmith/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/vpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/vpx,ShiftMediaProject/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,mwgoldsmith/libvpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,mwgoldsmith/vpx