Adding the PropertyEditor model as internal to slowly adopt it using a slightly different model approach then in v5.
Minor refactoring of IEntity/Entity.
Adding some notes and small change to IContentBase, PropertyValues and the ability to set property values with an anonymous object is shared for Content and Media.
Hiding language property untill its fully implemented.
Making set on Parent Id private.
Resolves a naming conflict in DocumentExtensions and DefaultPublishedMediaStore.
