Dump HTML/Image outputs in the workspace

Currently, our plugin is dealing only with the text outputs. Users may need to report/document their machine learning steps using images/HTML/graphs. This feature allows users to define a unit name to identify the HTML that belongs to the unit/step.

It creates a folder under the unit in the workspace and saves all the generated HTML/Images there. Then it can be used to report using report/publisher( eg. HTML publisher plugin)  plugins to create a report for the whole machine learning workflow.