Editing templates: when creating property template type lookup, offer a dropdown/typeahead of all the lookups we support

[michelleif]

in new version of Sinopia where you can edit templates like resources...
when you create a Property Template with type Lookup, you need to tell Sinopia where to lookup, by adding a URN from here: https://github.com/LD4P/sinopia_editor/blob/master/static/authorityConfig.json

can we instead just provide this list as a dropdown/typeahead for user to select from? rather than them having to go elsewhere to lookup the right URN and possibly mistyping?

[justinlittman]

This probably requires creating a new authority and changing the input to a Sinopia lookup component. This needs use the new SimpleList component.

[justinlittman]