Chromatic dispersion and line width phase noise

Chromatic dispersion and line width phase noise

Implemented CD and phase noise simulations and their corrections;
files written to (1) inspect waveform behaviour with time, and
(2) plot BER/SNR graphs. For CD, an extra file was written to
demonstrate (check) the pulse-broadening behaviour of the power
of the signal.

Code cleanup: move some code out to separate files for reuse;
renamed some variables for consistency; removed 3F4 PSK upper
bounds in graphs (bound too loose, not useful); removed isOctave
due to the current heavy dependence on functions not supported
by Octave.

TODO: put CD and phase noise together