remove RefAttribute and ManyRefAttribute
WiP: initial rewrite of Ref into IdView

an IdView is a entity mapper view of an entity, along with its entity id
update names, and fix some of the affected tests, but some have had to be commented out, due to the design change
corrected tests
Merge pull request #36 from pellucidanalytics/topic/refactor-Ref

Topic/refactor ref