Merge Johannes' changes into mine

I tried my best to merge Johannes' changes into what I have been working on.  The directory structure comes from running `cargo new 6502emu --bin`.  There is one unit test that can be compiled with `rustc --test -A dead_code 6502emu/src/main.rs`.
Not sure how I feel about LO/HI versus BEGIN/END for range constants. begin/end reminds me of the stl-style ranges where the end of the range is exclusive. LO/HI doesn't. Maybe we could make that a convention--LO/HI for inclusive+inclusive ranges, BEGIN/END for inclusive+exclusive?