Move preparation scripts into Docker container

[mabelzhang]

Currently, setting up vrx-docker requires the host machine to have the vrx (and vorc for the vorc branch) repo compiled in the workspace.

This adds a significant hurdle for teams to test their solutions against the evaluation, especially if the host is not Ubuntu 18.04, e.g. as reported in osrf/vorc-events#20 .

#26 has moved the log playback and video recording portions into the Docker containers.

Remaining to move into the Docker container are the preparation scripts and the corresponding instructions in the README.
That should cover everything.

This issue is considered done when the host machine is no longer required to have vrx and vorc compiled in order to run vrx-docker.