Limit the ability to double-submit forms

[fluffy-critter]

Often, a scientist will accidentally submit a form twice, resulting in duplicate data. To mitigate this, form submissions could have a randomly-generated transaction ID which gets added to a "recent transactions" table, and such submissions could check to see if the transaction already took place.

This would be particularly helpful in situations where there's no uniqueness constraint on the data being submitted (e.g. extractions).