Allow For Changing User Email Address

[alexbrdn]

sw360 should recognize when an email address of a user has changed and preserve the identity.

Criteria for email address change is that the Liferay user with the same externalId (field openId) has a different email address than the sw360 user with the same externalId.
Email change in Liferay is performed by LDAP importer or SSOAutoLogin action.

• when email changes, user's email should be updated and the old email moved into the list of previous email addresses of the user
• migration script necessary to replace all users' ids with generic ids instead of emails
• couchdb indexes should be build by field email address and by previous email addresses
• user search by email address should try searching by email address and fall back to searching by previous email address field

[maxhbr]

The same approach could maybe be used for licenses