Keys API changes (#4960)

Keys API changes (#4960)

* Add private information to the deploy keys api

This commit adds more information to the deploy keys to allow for back
reference in to the main keys list. It also adds information about the
repository that the key is referring to.

Signed-off-by: Andrew Thornton <art27@cantab.net>
* Add private information to the user keys API

This adjusts the keys API to give out private information to user keys if
the current user is the owner or an admin.

Signed-off-by: Andrew Thornton <art27@cantab.net>
* Add ability to search keys by fingerprint

This commit adds the functionality to search ssh-keys by fingerprint of
the ssh-key. Deploy keys per repository can also be searched. There is
no current clear API point to allow search of all deploy keys by
fingerprint or keyID.

Signed-off-by: Andrew Thornton <art27@cantab.net>
* Add integration test