Review FilteredTree and FilteredComboTree in org.locationtech.udig.style.sld

[fgdrf]

While reviewed #617 I stumbled about org.locationtech.udig.style.sld.editor.internal.FilteredTree and subclass org.locationtech.udig.style.sld.editor.internal.FilteredComboTree. Both having Eclipse file comments and seems to be copied from Eclipse.

Questions:

• Where are the differences to the origin files?
• Is the implementation of the current used Eclipse Framework better than the one we copied 12 years ago?

Intention: use Eclipse implementation if possible and remove copies from code-base.