GMTI Generator: better rendering in UI

I've been working on CGMTI Generator, to be more precise on UI part (sleazy JTree rendering, more details in this writeup). Now it's working much, much better: the whole data model for the tree is now a little more complicated (the lazy solution, converting to XML and displaying the elements as tree leaves turned out to be more costly when it came to editing - and displaying, especially large files).

Right now the model is returning regular GMTI package components (package header, all the segments, target reports). Before I had problems with slow rendering of those objects, but it turned out that I wanted to display too much. Right now I'm displaying only the most important information, and it's fast.

I plan to do some more last minute touches and post the new version (0.4) on the portal.