Validate new users

Adding a new user from the learner groups or instructors tab now
validates input for required fields, email address validity, and campus
id min/max length.
Validate instructor CSV upload
Validate learner CSV upload
Unset PDO connection on failures
Remove otherId from uploads

This was left around, but now that we are validating it needs to go.
Merge pull request #652 from jrjohnson/561-csvrefactor

Validate new Learners and Instructors