Absolute paths in documentation ToC

[kfhoech]

The documentation puts absolute paths in the user_guide_toc.xml file.

The documentation build should be modified to use paths relative to the workspace or plugin.

[kfhoech]

There are multiple problems related to this. First, the generation of the help table of contents in the simulator documentation suffers from absolute paths. We'll retain that issue. Second, for the AGREE documentation the table of contents is not generated at all. Enter that as issue #88. Finally, it appears that there is no generation of help documentation for the Test Case Generator. Enter that as issue #89