Allow updating multiple public sample information metadata via a single file

Discussing with @samd93 we think it would be ideal if we had a new "job" where a user uploads a single file to update multiple public studies with new metadata. This will simplify updating things for meta-analysis.

The catch is how to allow/verify-permissions. I guess my rules would be: no-deleting, updating or adding columns, etc.

@ackermag what do you think? 