Find duplicate Stanford applications and combine them

[epicfaace]

This happened because of the brief period in which people with Stanford accounts could create username+password accounts.

1. Find all username+password Cognito accounts ending in @stanford.edu and their corresponding applications.
2. For each of these applications, if there is a Cognito account with Stanford sign-on, then replace the ID in this application with that of the Stanford-linked Cognito account. Also, find the entry in the database corresponding to the Stanford-linked Cognito account, if it exists, and merge it with the previous record.