jdepend report improvements

submitted against the MAVEN project since maven-jdepend-plugin is not in the project list.

This patch fixes the following:

• lines in the jdepend report are actually double spaced since it uses <br> tags: xdoc converts them to <br></br> and bowsers interpretes them as 2 br. In the pathed <br> are replaced by appropriate html lists.
• general improvement in the html output: no font tags, thead/tbody sections, table summary, acronyms.
• empty package lists now properly display "none" as intended (there was a bug in the if condition test)