Refactor GetOSType, add WIndows 8/8.1
Update CS:GO, Dota 2 protobufs [ci skip]
Regen Dota 2 protobufs
Regen CS:GO protobufs
Update assembly info.
Add nuspec.
Update steamclient (beta) protobufs [ci skip]
Regen steamclient (beta) protobufs