WIP: Adding endpoint for log retrieval on the minion

Adding logic for retrieving logs from docker containers.
This commit is part one on the Accessible build logs card and contains only changes necessary to query minion for desired docker container logs. 

Usage:
`curl  http://10.245.2.2:10250/containerLogs?containerID=c93b7770a0b6`

The GoDoc is not missing, git moved it on the line 214 :)