retrieve allUsers, allOrganizations with single API call

- retrieves all users and all organisations by using the [/users api](https://developer.github.com//v3/users/#get-all-users) call. the resulting GHPerson list is available as well as the GHUser and GHOrganization list. call is used for GH enterprise integration into existing enterprise infrastructure.
- Fix repository ownership to return GHUser or GHOrganization.
- added suspend-at to GHUser
- added guava dependency