Started Exchange. Put buttons on Supply page for use cases.  Create exchange from the buttons.  Started the exchange logging page, barely.
Exchanges - added use case class, removed event type class, other misc.  Not working.
Merge branch 'master' of https://github.com/valnet/valuenetwork.git into exchange
Adding migration, should be in last commit.
add UseCase to admin
Exchange: in process changing to UseCase class, as far as can go without impacting existing code.
add description to work form and time worked to display on resource page
add url length validation on process logging page
add post_migrate handler to create or update UseCases
Merge branch 'exchange' of git@github.com:valnet/valuenetwork into exchange
remove errant pdb trace
replace PatternUseCase.use_case CharField with ForeignKey to UseCase
merge exchange branch into master