Feature/resource set

@barnabyalter I need to make the rake tasks work, but figured I'd open the PR to get some feedback/start a conversation sooner than later.

@NYULibraries/hydra please have a look and provide feedback as you see fit.
@scotdalton While I actually think this is a bug initially (it results in no identifier getting set for a record) this line did get lost in this changeover:

https://github.com/NYULibraries/ichabod/blob/19650b7b06738976d9639408b792e676cce70e42/lib/ichabod/data_loader.rb#L55

You could add it as another `before_create` to the FDA so it's still there and then we can ask @chrpr what the original intention was.