Implemented SSD, SAD and FindBestDisparity

Match costs may still be slightly off, but I'll figure that out later!
Fix indentation issues in SAD

Ugh.
Implemented NCC

Wooooo!
Implemented GaussianBlurMatchScore
Implemented BilateralBlurMatchScore

Adapted the implementation from the Assignment #1 solution, mehehehe.  I
should probably clean up the code so it looks less terrible though...
Cleaned up BilateralBlurMatchScore

It's not using ConvolveHelper, but it's much more in a form I'm happier
with.  Too bad Bilateral Blur isn't separable...oh well.
Implemented ComputeSegmentMeans
Implemented AssignPixelsToSegments
Fix memory leak in ComputeSegmentMeans

Ooooops!
Implemented SegmentAverageMatchCost
Tweak image pixel intensity calculations

Apparently SSD and SAD needed some tweaking to get the results into
acceptable ranges.  The homework suggests we need to be able to generate
images with errors below a certain threshold, and I needed these tweaks
to be able to hit that.  I understand removing the 0.3/0.6/0.1 part for
intensity calculation, but I'm less happy with adding a sqrt for SSD,
since I don't know where that idea came from.  But someone on the forum
suggested it, and the TA seemed to concur, so who am I to argue with
wishy-washy logic like that.

The README presumes I'll use a late day on this, which I am likely to do
(so that I can finish the written assignment, booooo large papers).
I'll update it if I need to.
Check-in written responses for Assignment 3

Ugh, it hasn't been long enough since the last time I had to analyze
academic papers (especially long-winded ones).  At first I wanted to
take these seriously, but...

Crossing my fingers that Assignment 4 doesn't have anything silly like
this again.
Assignment #3 complete!