Start passing along ent cert ssl info to ostree

Add some models for the ent cert -> contents
mapping..

Move repolib's get_key_path to utils, and use
it for ostrees info.

Add 'tls-client-[cert|key]-path' to OstreeRemote
Mock an ent cert associated with a content.
Save needed ostree remote info to config file.
repr and report format cleanups.