Rearranged starter process flowchart and added sidebar

- Rearranged to make sure ready check comes before feeding.
- Simplified by removing Discard block, and shortening titles.
- Details moved to legend box below.
- Changed arrowheads to be cleaner "Latex" style.

book/figures/flowcharts_tikz.tex

@@ -1,6 +1,6 @@
 \tikzstyle{every picture}+=[font=\footnotesize\sffamily]
 \usetikzlibrary{calc, shapes, arrows, decorations.pathreplacing, calligraphy,
-                positioning}
+                positioning, arrows.meta}
 \tikzstyle{decision} = [diamond, draw=codeblack, fill=codeblack, text=white,
     text width=4.5em, text badly centered, node distance=3cm, inner sep=0pt,
     line width=2mm]