Two potential bug fixes: Error W0102 from pylint - don't make default
variables equal to [] in function headers.  This has the potential to
cause bugs.  See pylint W0102 for more information.
Also removing unnecessary semi-colon.  Comment longer than the change.
Remove unused variables from function in PlotUtilities.
Undo bug fix: string has a .printables set that can be used for checking
for unprintable characters - str does not.  Allow use of import string
for this purpose only - ignore warning W0402 from Pylint.
Scatter plot docstring.
Fix imports in AddChrPrefix.
Fix missing system path
Test for input file's existance before running anything in the Wave
Generator.
Avoid pylint W0631 by not reusing variables.
Avoid possible reuse of variables in Compare wave sets, remove unused
debugging lines.
Remove sample_id from make_gausian in SVGPlot and ensure all variables
in self are declared in __init__.
Don't overwrite variables from main scope.
Remove unused debugging statements.