start splitting up gui/constants: remove unneeded import
gui.py: use units.M
gui/constants: remove gui init constants
fix init_rbw units
move plot widget constants to plot_widget
remove unnecessary import
remove device "constants" from gui/constants
move trigger type constants to pyrf.config
move RBW_VALUES to the one module that needs it
move GUI labels to labels.py
gui colors in colors.py
pep8: uppercase class names
bug fixes