Fixes issue with deleting content types that have content
Ensures that the ContentBase item is set on Document/Media and that the property value is set based on the already loaded value in the model if IData implements IDataValueSetter (which DefaultData does). This streamlines how properties get their data and will save on a ton of queries when using the legacy API.
Cleaning up a bit of the legacy member class

Conflicts:
	src/umbraco.cms/businesslogic/member/Member.cs
Updates legacy Member class to setupNode based on the new IMember object (just like we do with media/content) - this will speed up data retrieval and is the start of wrapping the new API from the old one.
adds Exists(string username) to member service and wraps IsMember with that call.
Merge remote-tracking branch 'origin/6.2.0' into 7.0.1

Conflicts:
	src/Umbraco.Core/Persistence/Repositories/Interfaces/IMemberRepository.cs
	src/Umbraco.Core/Persistence/Repositories/MemberRepository.cs
	src/Umbraco.Core/Services/MemberService.cs
	src/umbraco.cms/businesslogic/member/Member.cs
Strange, somehow these updates got overwritten
Merge remote-tracking branch 'origin/6.2.0' into 7.0.1
puts IDataValueSetter back in so it can be used by backwards compatible data