fetch ICSharpCode.SharpZipLib from nuget
fetch MaxMind.GeoIP2 from nuget
fetch SharpFont from nuget
fetch NUnit 2 from nuget
fetch SDL2 (native Windows DLL) from nuget
fetch Mono.Nat from nuget
add the intro videos to the first missions
Merge pull request #7196 from Mailaender/prologue

Added the intro videos to the first missions as background info
Merge pull request #7197 from Mailaender/nuget-thirdparty

Cleaned most of the thirdparty folder from foreign binaries
Update INSTALL.md

try to explain the changes from #7190 and #7197
this has already been resolved in #7121 and #7187
StyleCop
register Linux MIME type to directly load replays
save replays in a less generic file extensions