U4-1083 - proper error message on content type alias duplicate
Merge remote-tracking branch 'origin/7.1.9' into 7.1.9

Conflicts:
	src/Umbraco.Web/umbraco.presentation/umbraco/create/nodeType.ascx.cs
Merge branch '7.1.9' into 7.2.0

Conflicts:
	src/Umbraco.Web/umbraco.presentation/umbraco/create/nodeType.ascx.cs