Simplify makeRhs and applyLhs

The if tests were redundant, because the top and bottom shifts were set
to zero in the smoother. Much simpler now!
Use double precision.

Need double precision so that exponential gain after inverse FFT does
not boost up rounding errors.

Added an option for a Ricker wavelet with specified peak frequency.

Added a demo script that compares modeled seismograms with simple
summation of time-delayed wavelets in the case where Q is infinite and
reflection coefficients are small, so that multiples are negligible.
Tweak demo parameters.
Implement and test pseudocode in report
Add testSpd methods for debugging slow convergence.

Tests seem to pass, but will leave them in there for now.
Flatten the GBC 3D P-wave image.
Make images of conical faults in cylindrical coordinates.
Experimenting