Style fixes to BBox, update copyright header
BBox: Always offset the top border by the same amount

...so that the top border of BBox's with no labels, BBox's with
text labels, and BBox's with BControl labels will all line up.
Screen: Undo hack to line up the top borders of the BBox's

Also, use font relative spacing units
Appearance: Use font relative spacing insets for the preview boxes

Set the top inset to 0 since BBox's now have a natural top offset.
Backgrounds: Use font relative spacing and adjust insets

BBox's now line up.

Once again set the top inset of the BBox that forms the main
backgrounds view to 0. This should probably be converted to
a BView...
DebuggerInterface: reset port IDs on Close()...

...and add accessor to detect whether we currently have a valid
connection or not.
TeamDebugger: minor cleanups.

- On team exit, close the debug interface.
- When receiving a restart request via the listener, save settings
before dispatching it.
BreakpointManager: Adjust breakpoint installation logic.

If the debugger interface isn't currently connected, don't attempt to
actually install the breakpoint, and simply consider the operation a
success. This allows setting new breakpoints after e.g. the team has
exited.

Resolves remaining part of #9774.