Check if enough file space is available while downloading packages

Summary

I tried to install Duality on an other computer. DualityEditor crashed because I hadn't enough file space on this computer.

The eventviewer displays this stacktrace:

Application: DualityEditor.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.IO.FileFormatException
   at MS.Internal.IO.Zip.ZipArchive.OpenOnStream(System.IO.Stream, System.IO.FileMode, System.IO.FileAccess, Boolean)
   at System.IO.Packaging.ZipPackage..ctor(System.IO.Stream, System.IO.FileMode, System.IO.FileAccess, Boolean)
   at System.IO.Packaging.Package.Open(System.IO.Stream, System.IO.FileMode, System.IO.FileAccess, Boolean)
   at NuGet.OptimizedZipPackage.EnsureManifest()
   at NuGet.LocalPackageRepository.OpenPackage(System.String)

Exception Info: System.IO.InvalidDataException
   at NuGet.LocalPackageRepository.OpenPackage(System.String)
   at NuGet.LocalPackageRepository.GetPackage(System.Func`2<System.String,NuGet.IPackage>, System.String)
   at System.Linq.Enumerable+WhereSelectEnumerableIterator`2[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]].MoveNext()
   at System.Linq.Buffer`1[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]..ctor(System.Collections.Generic.IEnumerable`1<System.__Canon>)
   at System.Linq.Enumerable.ToArray[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]](System.Collections.Generic.IEnumerable`1<System.__Canon>)
   at Duality.Editor.PackageManagement.PackageManager.get_IsPackageSyncRequired()
   at Duality.Editor.Program.Main(System.String[])