Fix transition smartdown flow lookup
Add a smartdown rake task, for renaming flows

As the flow directory name and coversheet name need to stay in sync
Rake tasks to convert smartdown flow state/name for trasition
Convert student-finance-forms Smartdown flow to transition

Renaming the flow to have '-transition' is the simplest way to let us run Smartdown
flows against regular flows without name clashes. This is a bulk rename as the app
and Smartdown kind of expect the flow name to match the directory/coversheet path.
Refactor Smartdown registry to treat transition like draft status

Transition flows, by convention, have a '-transition' suffix to distinguish them from
the original smart_answer version.

When in transition we always want them to be available on preview, so
treat them the same as draft status
Merge pull request #1106 from alphagov/transition-status

Make Smartdown flows with transition previewable