Distinguish privacyIDEA and non-privacyIDEA token

[nilsbehlen]

Add a flag to the token to distinguish the two categories. This can be handy later to offer different or additional features depending on the category. Possible indicators that a token is a privacyidea token:

• issuer=privacyIDEA (make check case insensitive!)
• Usage of new url scheme (pia://...)