Fixed formatting for PDF.

I finally learned that the raw cells let you put latex directly
into the output. So now I have the appendix being created without
the [1] %%latex showing up in the output. Also wrote code to parse
the .tex file to make the Preface a chapter without numbering, so it
is now a proper preface, and not "chapter 0".

I have not touched the Windows generation tools, so PDF generation
in Windows is now broken. I don't think I care.

pdf/to_pdf.py

@@ -0,0 +1,13 @@
+from __future__ import print_function
+import io
+
+import IPython.nbconvert.exporters.pdf as pdf
+import fileinput
+
+for line in fileinput.input('Kalman_and_Bayesian_Filters_in_Python.tex', inplace=True):
+    print(line.replace('\chapter{Preface}', '\chapter*{Preface}'), end='')
+
+
+p = pdf.PDFExporter()
+p.run_latex('Kalman_and_Bayesian_Filters_in_Python.tex')
+