Fix monitor port cmdline args checking.
Hide local reporting files inside a directory.

These are non barn-agent core files and makes it clearer they are
just for sending metrics.
Add barn monitor comment.
Finish separating metrics reporting from implementation.

Help differentiate the agent code from the barn-monitor app code and also
allow plugging in other telemetry implementations at some future point.
Finish separating metrics reporting from implementation.

Help differentiate the agent code from the barn-monitor app code and also
allow plugging in other telemetry implementations at some future point.