Fixed error combining CCD x coordinate to stage coordinates when CCD is
facing an arbitrary angle for all permutations of stage ordering.

Solution depends on custom levi-civita symbol implementation.
Changed exit code for mirror scan script to 0 for normal exit and 1 for any error.
Created an intrument initialization function 'itop.instrumentation()' that can be used in production code to supercede the debugging-use-only function 'itop.initialize_instruments()'.
Improved prism angle function symantics. Added utility functions for prism testing including a means of calculating the angle directly from a pair of beam objects.
Initial commit of prism scanning code ported from B. Pal's script.
Added prism edge finding routine to prism scan code.
Added function to check if a value is with stage limits to the Limits class.
Prism scan range input now covers intended beam input x positions as measured from S6 instead of raw prism stage x positions. Any position that cannot be reached by the stage is removed from the requested samples.
Changed default sample range to reflect new range input meaning. Default range is to scan the full the prism up to 5mm from each edge, if possible. Also, adjusted profiler power thresholds to ignore autocollimator during search for undeflected beam. Power levels are restored after the beam is found.
Using global itop module constants for default refraction indexes.
Fixed error in method declaration + PEP8 fixes.
PEP8 fixes.
Fixed bad call to first sample point. Displaying beam input x position as measured from S6.
Fixed wrong call to dispersion correction functions (wavelength nm -> um).
Changed docstring for scan mirror function.