Add VS files and quvif code

quvif is more like prototype for now, albeit a working one
Add initial .gitignore
Use #pragma once instead of #ifndef in streams.h
Don't disable warnings globally in streams.h
Alter AMOVIESETUP_FILTER struct a bit

And make it default-constructable
Extend .gitignore with VS stuff
Don't return prematurely when reading debug level

DirectShow logging now works as expected without admin rights
Import libdash project
Point libquvi-scripts submodule to new fork