4233: "helper" method for replaying a job log from a specified file, with utility rake task
4233: correction: the 'text' in the properties hash when simulating a logged event should be the entire log file line verbatim
4233: (naive) first iteration at graphing job log stats
 - does not update, but graphs the story so far
 - does not do scaling
 - has no error checking
4233: redraw graph when processing log events
 - still very naive
 - still does not scale y-axis
 - does not try to limit x axis timeline to 20 minutes: just keeps growing
 - seems intolerably inefficient - optimization on several fronts almost certainly still required:
   - initial draw on first page load should do much less client-side processing
   - at accelerated speeds, it cannot keep up, and if we expect so much data throughput we'd want to devise a way to only redraw once in a while to save needless processor work
4233: why pass around global variables?
4233: now the y-axis series will scale to always be between 0 and 1
4233: keep graph data array sorted by timestamp
4233: remove explicit JS includes for showing Keep histogram now that they are in the general assets
4233: will rescale y-axis for a series that scrolls off leaving less than fully scaled data points displaying on the chart
4233: only redraw graph a maximum of once every 5 seconds
4233: do not scale the 'cpu' series stats, and divide them by cpu count
4233: bug fix - rounding errors were causing us to miss maxima scrolling off the chart, and rescaling was not occurring
4233: chart stats for parallel tasks separately
  - this commit also extends the scroll time to 10 minutes
4233: show original data in hover info instead of proportions
4233: better labelling includes raw interval data and number formatting
4233: catch and ignore log processing errors
4233: simple but reasonably effective tests
4233: In crunch-dispatch, log timestamps in UTC in the same format crunch-job uses.
4233: add deletion of existing log entries option to log replay helper and rake task
4233: show empty log stats graph when no data, and also show a full width x-axis (currently 10 minutes) even when only a few data points have been plotted