Create abstract base freemix.exhibit.models.DataTransaction to be used for asynchronous data transformation and augmentation. Create viewshare.apps.upload.models.UploadTransaction to handle transformations with Akara.
Create freemix.exhibit.models.ExhibitProperty and Property Data models asyncronously.

Create data migrations for freemix.exhibit.models.DataTransaction and
upload.models.UploadTransaction.
Merge branch 'feature/new_datamodel' of github.com:LibraryOfCongress/viewshare into feature/new_datamodel
Merge remote-tracking branch 'upstream/feature/new_datamodel' into feature/new_datamodel
add data serializer, ensure records have id's, adjust upload pipeline to use serializers, minor bug fixes