- TKinter code is now in PresentationLayer.init_gui()
- aligned things better on the grid
- added placeholder widget for parser hierarchy information

Backend support for parser hierarchy widget

- left hand side shows the parser about to be invoked (top of current parser stack), as well as its address
- right hand side shows the current position in the input + the next 32 bytes
- step button executes hammer-parse-step 1

Start the GUI by sourcing gui.py after parser-name-instrumentation-gdb.py and utility-commands.py have been loaded