PASTA: Need to check whether the dataset is present in PASTA before submission

[isangil]

PASTA's API contemplates the create-new dataset and update operations - these are called differently.

it would seem currently that updates to dataset send to PASTA's create-new, creating a silent rejection, or at least a rejection that is not recorded. we'll need to check whether the EML is in PASTA before deciding the type of submission we do.

This is not critical, and largely irrelevant to non-LTER users, who should not activate the PASTA module.