Extend comment support to indirect work items

[pellecchialuigi]

Currently BASIL support comments on work items directly mapped to the reference document.
It should be possible to comment also a work item nested as child of a directly mapped work item.
So, to be more clear, if for a software component we have a Test Case nested under a Sw Specification nested under a Sw Requirement that itself is nested under another Sw Requirement, it should be possible to manage comment to each of the above mentioned work items.