Remove commented code and comment cruft

* Remove commented-out code; code can be restored later from earlier
  commits if need be.
* Remove initial and terminal empty lines from doc comments.
* Convert /** comments that aren't doc comments to line comments.
* Convert other multiline comments to line comments.
* Remove "non-javadoc" comments added by Eclipse. Supposedly, the
  rationale for the comments was originally a bug in Javadoc. I have no
  idea why they're still around: they aren't consumed by Javadoc so they
  serve no end-user documentation purpose; developers can easily jump to
  the superclass definition with Eclipse; and all overridden methods
  should be marked with `@Override` anyway.
* Remove empty Javadoc comments.
* Remove empty Javadoc @fields as they take space and are uninformative.
  More importantly, they still cause the Javadoc validator to issue a
  warning. Thousands of these warnings make it impossible to find a
  legitimate Javadoc warnings like broken markup and references.