Add assignment 1 files

Add assignment 1 description and Matlab files. Matlab files Ass1.m and
covar.m are incomplete.

Add test script to compare performance between Matlab built-in function
xcov() and assignment 1 function covar().
Update notes for section 1b

Add relation between cross-correlation and cross-covaraince notes for
part 1b.
Add GNU Octave compatible version of Assignment 1

Replace simulation of Simulink model with functions tf() and lsim().
Since use of xcov() requires loading of the signal package in Octave,
a check for 'OCTAVE_VERSION' determines if the package is loaded.

Note: Using Octave requires the packages control, general, and signal.
Reimplement cross-covariance using fft

Calculate cross-covariance using a fft based approach. Rename function
from covar() to crosscov() due to name clash with MATLAB builtin
function. Update test script to display size of input.
Fix shape of bias vector
Add Matlab code for Assignment 1, Question 2

Add Matlab code to Assignment 1 script for Question 2 and the beginning
of Question 3. Minor changes to Simulink model, notes, and script for
testing cross-covariance.
Add Matlab code and notes for question 3

Calculate models and generate plots for 3b, 3c. Add notes for response
to 3a, 3b, 3d. Remove iffshift() from power spectrum calculations in 2c
as the frequency vector ranges from 0 to 2*tau and the Fourier transform
of the various cross-covariances should not be centered around 0 Hz.
Correct model selection for system in question 3b
Save all figures to eps files

Add eps_save() function to save figures as files and save all figures in
assignment 1 Matlab script.
Change plot labels and plot settings

Increase linewidth for plots and standardize colors. Change plot labels
to be more descriptive.
Add LateX file for assignment 1

Add incomplete .tex file for assignment 1. All Matlab figures are assumed
to be located in directory tex/images due to errors with .eps to .pdf
conversion.