Support for get all permission targets

[simonstumpf]

Is your feature request related to a problem? Please describe.
The Artifactory REST API has a endpoint which returns a list of all permission targets.
Unfortunately this library doesn't support this endpoint, you can only return a single permission target.

Describe the solution you'd like to see
A method like GetAllPermissionTargets.

[mihir-io]

Just wanted to add that I ran into the same issue recently. Would be great if we could get a fix!

[eyalbe4]

Since the team is loaded with multiple other initiatives and to expedite the implementation of this requirement, we would welcome a pull request that adds this.