Breakpoint window

This adds a window for defining breakpoints, opened by clicking on the breakpoint button in the disassembly view.
The whole dialog content is evaluated, but a few things aren't loaded from or saved to breakpoints/memchecks yet because they have yet to be fully implemented there.

![psp5](https://f.cloud.github.com/assets/4809758/733387/e4201d70-e29c-11e2-84cd-a26c29990134.jpg)