Event handlers dependent on IP or user

[cornelinux]

We could make event handlers dependent on users or IPs.

Well, actually we might also think about using the same conditions for event handlers and for policies.

Could we build some kinf of a conditions class, that would apply for both?

See https://community.privacyidea.org/t/event-handler-for-specific-user-s-or-ip-s/934

[cornelinux]

We will deal with the generic condition idea in #1436.
Here we simply add for event handlers:

• resolvers
• IPs