VM CLI: set ip

[ixje]

I think it could be useful to have a command that allows for setting the instruction pointer. Right now you can load a nef, but run will always execute whatever function or code is at offset 0 (obviously). Having the ability to set the instruction pointer we could at least call some other functions (the offset can be grabbed from the manifest). Of course it's still limited to functions without arguments but that could be all you need sometimes.