[GenericDepthPlugin] More compatibility (Few UE3 games)

More compatiliby by adding an option 'ZBufClearIndex'. Works really well here.

I haven't added the 'martinsh_ssao.fx' shader (which you'll see incorrectly labeled as 'MSSAO') because it won't work right now. I'll add it tomorrow. It's not the best AO but it's really fast and handy

I might have added project files again. Weird because I always make sure to exclude them. Damn Git !

EDIT : I tested your changes in VSSAO2.fx. The pow(z, 36); is really interesting. I couldn't have come up with that myself for sure :)