update version to 4.4.2

Update appveyor.yml

Update CHANGELOG.md

update changelog

Merge pull request NLog#1796 from NLog/improve-test-performance

Improve unit test performance

Merge pull request NLog#1749 from NLog/fix-UnauthorizedAccessExceptio…

…n-Android

try-catch for permission when autoloading

Update project.json

fixed unstable InternalLoggerTests.TimestampTests (NLog#1739)

* fixed unstable InternalLoggerTests.TimestampTests

* setting default timesource after internal logger tests

update build script for nlog 5

Fix memory leak in AppDomainWrapper (NLog#1690)

* Unsubscribe from AppDomain when closing down

* Breaking change where AppDomainWrapper no longer attaches itself to the AppDomain

* Non Breaking change where AppDomainWrapper performs lazy attachment to AppDomain