Moving GenericFile::Webform

Files in the ./sufia-models should not reference any files outside of
that directory.
Adding a partial to allow for overriding batch_edit menu actions.
Merge pull request #118 from psu-stewardship/be_action_override

Adding a partial to allow for overriding batch_edit menu actions
Merge pull request #117 from projecthydra/moving-generic-file-webform

Moving GenericFile::Webform