fix(ssh): format host entries in known_hosts correctly

This change also adds sshDefaultPort in the ssh module only if necessary
rather than tacking it on arbitrarily in fleetctl.
refactor(ssh): improve known hosts handling to better match spec
chore(ssh): add LICENSE information
chore(ssh): change comments to slashes
refactor(ssh): remove unused code, clean up
chore(ssh): switch to glog
chore(ssh): switch to glog
refactor(ssh): split out match/matchHost to separate files
fix(ssh): fix tests, further cleanup for simplification
fix(ssh): finish docstring
Merge pull request #410 from jonboulle/410

fleetctl appends port number in ~/.fleetctl/known_hosts