Use PropertyEditor Resolver in favor of static mapping file
Changed data types storage to store guids instead of ids.
Update test to match new converter behavior (null -> empty Archetype)
Extract & Wrap PropertyValueConverter method to fix tests

Unable to access PropertyValueConverterResolver.Current from a test, so wrapping in a quick check for UmbracoContext.  Probably not the best fix, but wasn't sure best way or if overkill to create an abstraction.

Also extracted the logic that finds/executes PropertyValueConverters to make testing easier.
Merge pull request #95 from imulus/fix/tests

Fix Fieldset tests
Added a "start with Add button" option that shows "+ Add" instead of default fieldset.
Update the GUID, seems to not default properly at times
Merge branch 'pr/94' into develop
Merge branch 'develop' into pr/96
Fix a glitch that won't let a single fieldset be removed if multiple FS's are configured with the 'Start with Add' option
Merge branch 'develop' into feature/discover-datatypes

Conflicts:
	app/Umbraco/Umbraco.Archetype/Api/ArchetypeDataTypeController.cs
Update core references to 7.1.0
Remove reference to old config file
Merge branch 'develop'