Add task result graphic ploter command

$ rally task plot2html --task-id <uuid> [--out filename.html] [--open]

* Get results of task with <uuid>
* Process it
* Write results to filename.html if it is specified or
  to the <uuid>.html
* If --open is specified file with results will be opened
  in your web browser

In HTML file with results we have:
* Select box that allows to specify benchmark from task
* Dump of JSON config for this task
* Stacked area graphic with duration and idle_duration for every iteration
* Pie with ratio errors/success
* Stacked area graphic with duration of all actions
* Pie with ration between avarage time of actions

This is only first step. In future we should:
* Add results in text represenation (e.g. our CLI task detailed)
* Add raw results
* Add histogram graphic that will show probability / duration for duration and atomic
  actions.

bp data-processing

Change-Id: I1168c6c85816bb26ef1637a385c8ccc558d8d1d7
Merge "Add task result graphic ploter command"