Update changelog

Update changelog for 4.4.0

Update changelog for 4.3.1

Add 4.3.0 version header with release date

Add 4.2.1 to changelog

Fix explicit NuGet version tool corrupting package

UTF-16 in the nuspec won't load with NuGet, so force it to UTF-8.

Update changelog for 4.1.1

AppVeyor automatically excludes gh-pages

Fix nuspec for log4net version

Update changelog for 4.0.0-beta002