#3 Improve the debugger GUI

[Anton]

The debugger is controlled via a command line, but some of its functions would be more efficient if they were made accessible via the GUI:
1. Setting and removing of breakpoints could be done by clicking on the desired instruction in the Disassembly window. This would be a lot faster that typing the command and address and pressing Enter.
2. The disassembly window could be make scrollable (via a scroll-bar), and the "di" command could be implemented via a key combination like CTRL-G (for "GO to ADDRESS", asking the user for the destination address in either HEX of decimal notation (with two parallel edit boxes).