Provide contextual remove breakpoint in stack view

Once a breakpoint has been hit, it is usually possible to remove the breakpoint by clicking the left ruler of the JDT editor; good.

However if the breakpoint is stale, the displayed line may not be compatible with toggling. It is therefore necessary to traverse the breakpoints view to find the file line and then remove it.

Particularly confusing is when the stale breakpoint is displayed on the closing method brace. In this case toggling to 'remove' the line breakpoint actually creates an exit breakpoint, which not only fails to remove the breakpoint but also switches the debugger into its devastatingly slow interpreted execution mode.

If the stack view had a remove breakpoint option, it would all be much easier.