Document properties [WIP]

Fixes #3202. Feedback is appreciated!

- [ ] Design an icon for the secondary toolbar.
- [ ] Develop a method to parse the PDF date string format (see http://res.icesoft.org/docs/icepdf/latest/core/org/icepdf/core/pobjects/PDate.html for more information). Not sure how to deal with country-specific ways of displaying dates yet.
- [ ] Can we remove the printed metadata string from the console output once this lands?