Bug_Submitter: add javadoc and authorship info
Bug_Submitter: split validation to its own method
Bug_Submitter: move inner classes to separate files
Bug_Submitter: update copyright year range
Bug_Submitter: fix a bunch of Eclipse warnings
Bug_Submitter: move system info to uneditable pane

There is no reason the user should be changing it. Having it separate
also makes it easier to verify that the user actually typed in a valid
description.
Bug_Submitter: remove obsolete dummy text

The explicit error checking now requires the user to fill in the summary
and description, so there can be no chance of submitting a bug report
without these fields populated (at least superficially).
Bug_Submitter: visually flag invalid fields

This is hopefully clearer than just complaining about the first invalid
field, since it flags *all* invalid fields, and the flags do not
disappear until the user at least focuses each invalid field.