incorporate ps4 into notes collection.  add script to add mathematica notebook metadata fragments to descriptive index.
DFT notes.

modified:   ../METADATA
new file:   discreteFourierRangeFig1.eps
new file:   discreteFourierRangeFig1pn.png
modified:   discreteFourierTransform.tex
modified:   renumber
modified:   ../phy487/condensedMatterProblemSet4Problem2.tex
new file:   ../phy487/mathematica/discreteFourierRangeFig1.nb