Fixes naming conventions from old Notification class
Created notifications repository and service with unit tests, then need to start integrating that so notifications are properly sent.
Merge remote-tracking branch 'origin/6.2.0' into 7.0.2

Conflicts:
	src/Umbraco.Core/Umbraco.Core.csproj
	src/Umbraco.Tests/Umbraco.Tests.csproj
	src/umbraco.cms/businesslogic/CMSNode.cs
fix merge issue