Convenience find_by methods #402
Description
As a foundry dataset user I want to easily be able to find a dataset by DOI or by source_id so I can go directly to my dataset of interest
Description
Add find_by_doi and find_by_dataset to the Foundry class.
These methods return a single Dataset instance
Assumption
- if the source ID or DOI don't exist, throw an informative exception
Acceptance Criteria
f = Foundry()
ds = f.find_by_doi("DOI12/344")
ds2 = f.find_by_source_id("1233423")
f.find_by_source_id("doesnotexist")
f.find_by_doi("doesnotexist")