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`

Well done with the `flushWriter`! This is something that upstream might be interested in as well.