Force NUnit tests
Revert "Force NUnit tests"

This reverts commit 3cac96e3caf071540e106e31c6cbef95aa186d37.
Force NUnit tests in test projects
Remove System.IO.Abstractions from package.config
Revert "Force NUnit tests in test projects"

This reverts commit d04f44a95a347ed3d27a5d7225976ebe9f77a21f.
Add XUnit from NuGet
Convert to XUnit part 1
Convert to XUnit part 2
Adapt tests
	Converted last test
Cleanup NuGet packages and add XUnit to projects
Fix project file
Merge branch 'master' into CodeBetterBuildServer

Conflicts:
	tests/NLog.UnitTests/Config/TimeConfigurationTests.cs
	tests/NLog.UnitTests/Targets/Wrappers/AsyncTargetWrapperTests.cs
Merge branch 'master' into CodeBetterBuildServer
Fix tests after merge
Merge branch 'master' into CodeBetterBuildServer
Merge branch 'master' into CodeBetterBuildServer
Merge branch 'master' into CodeBetterBuildServer
Merge branch 'master' into CodeBetterBuildServer

Conflicts:
	tests/NLog.UnitTests/LayoutRenderers/AppSettingTests.cs
Use XUnit to run tests on server