Debugger: Fix memory display

- Watchwindow: Do not open Address dialog if menu is canceled (act = 0
  matching the unitialized unknown memory action)
- Actually pass the address of the dialog to the agent
- Make the "Open Memory editor..." action always visible to be able to
  look at const char *x pointing at y
- Improve the address dialog with checking and dialog button box
- Explicitly pass the quint64 around
- Translate & purge