Displaying PDFs (#109)

A basic ICEpdf preview. Mind the dependency license (Apache).

Using 5.0.5 since the latest 5.0.6 isn't in the maven repository. They don't use Maven central but a private repository for some reason.

The code is rather basic, I wasn't sure what to put in generateInfoPanel.

BTW, the PDF viewer need a lot of screen real estate. So it will look odd when multiple nodes are selected.