Change registration email logic

Use select2 multiselect text field for entering custom email addresses. Keep
track of all email addresses that have been used for a program and always send
email to these addresses whenever the program gets reclassified. Allow
classifier to only add new custom emails.
Remove .required-pseudo from validation selector and make register-button bigger
Do not send email to the classifier (only to the previous one)
Show previous classification criteria in email and change wording a bit
Move if-expression out of the template
Show series and episode name in registration email when set
Fix bug where root edit mode would crash if there were no classifications
Remove unused CSS rules
Merge branch 'master' into registration-emails-refactor

Conflicts:
	server/schema.js
Merge pull request #37 from kavi-fi/registration-emails-refactor

Registration emails refactor