Enhance Insight Collector generated HTML reports

During #456 (closed) and related issues demo (as well as in other subject-related discussions), multiple enhancements were proposed for the Insight Collector generated HTML reports:

• Currently, when no test data matches report scope, no report is generated. It could be interesting to generate, in lieu, a html file with respective warning message.
• Error block placed at the end of the HTML report should be moved at the top to be more visible.
• spec.template items should allow for warn-if-not-found and skip-if-not-found properties. In this way, the user can choose if he wants to have warning messages in his report when item is not generated (i.e a table listing failed test cases only).
• test.data column fields should have a truncated mouseover displaying dataset items.
• Table flexibility should be checked: currently, in Squash carousel, large table do not fit into the frame.
• Doughnuts display in Squash carousel must be fixed.
• Clickable elements must have more explicit style (underlined).
• When multiple pop-up windows are opened, "Cancel" button could close them all.