Allow users to update their email and other account details

[bsnouffer]

Users should be able to update their email and other attributes about the account. We could also allow for users to select a username besides their email. This came up when a user requested to update their email because they switched jobs and their account was tied to their work email, which they no longer have access to. While the email is not used for much in the Tool currently, it is used for password recovery so if a user forgot their password in this situation they would be locked out from their account.

This would potentially require migrating to a new AWS user pool. An added bonus of doing this is that we could make usernames be case insensitive in the new pool. (The setting is new this year and you can't update the setting once the pool is created so unfortunately usernames are case sensitive currently (see #263))