Debugger

Support the usual real time debugging tasks, such as:
* Launching a program
* Connecting to a local or remote debug server (e.g. gdbserver)
* Stopping/Stepping/Continue program execution
* Set breakpoints
* Inspect (and modify) machine state

IDA's interface:

There is likely behavior here we may want to push into angr, and it will require some more thought. Capturing here as I plan to work on this in the near future.