Initial implementation of exception configuration window.

Doesn't actually take any actions yet, just presents a UI.
Slightly rearrange BreakpointsView.

Line up the buttons along the bottom rather than the side.
Add button to invoke exception configuration window.
Add hooks for actually showing/managing exception config window.
Implement throw exception breakpoints.

The exception thrown checkbox now tries to set/clear breakpoints for
gcc2/4's respective exception throwing functions. Some tweaking still
needs to be done in order that these aren't visible in the breakpoints
list like normal user set breakpoints.
Add hidden attribute to UserBreakpoint.

Marks a breakpoint as one that should not be exposed in the UI's normal
breakpoint management interface. Adjust settings management to
preserve/restore appropriately.
Extend UserInterfaceListener to allow marking...

...breakpoints as hidden. Adjust TeamDebugger accordingly.
BreakpointListView/SourceView: ignore hidden breakpoints.
ExceptionConfigWindow: detect current exception status...

...on startup by seeing if the breakpoints for the exception functions
are already installed or not.