make the handbook compile on modern LaTeX distributions

TeXLive 2016 complains about \it and \bf.

Also, this patch adds a simple bash script to create the handbook from
its LaTeX sources. Note that this script does *not* attempt to detect
if all prerequisites (in terms of binaries and LaTeX packages) are
properly available.

doc/handbook/newton-in-a-nutshell.tex

@@ -7,7 +7,7 @@ conservation equation needs to be solved:
   \frac{\partial \phi \varrho_\alpha S_\alpha}{\partial t}
  -
  \text{div} \left\{
- \varrho_\alpha \frac{k_{r\alpha}}{\mu_\alpha} \mbox{\bf K} \left(\text{grad}\, p_\alpha - \varrho_{\alpha} \mbox{\bf g} \right)
+ \varrho_\alpha \frac{k_{r\alpha}}{\mu_\alpha} \mbox{\textbf{K}} \left(\text{grad}\, p_\alpha - \varrho_{\alpha} \mbox{\textbf{g}} \right)
  \right\} - q_\alpha} _
 {\textbf{f}(\textbf{u})}
 = 0 \; .