removed old plotting mechanism, added pyqtgraph to plot, added max hold and grid hotkeys
added trigger controls
began adding a hotkey dictionary
finished adding triggers, added arrow controls, added center freq arrow control, if/rf gain arrow controls, began working on markers
start of 0.5.0-dev
document new installation requirements for pyqtgtaph
remove generated pyrf.egg-info directory
add pyrf.egg-info to .gitignore
remove windows-only msvcrt import
comment out missing _delta_control hotkey function
Merge branch 'implement_pyqtgraph' into implement_pyqtgraph_cleanup

Conflicts:
	gui-requirements.txt
	pyrf/gui/gui.py
began implementing markers/peak finder
finished peak/marker functions, peak will be restrained by trigger area
start of sweep device code
fix SweepEntry doc
improve plan_sweep docs
document device attributes used
WSA4000: add sweep device constants
minor fix implemented to peak/marker, marker can now be clicked
plan sweep first simple test