extended documentation for scalar example
improved docu for scalar example; added ** at several points
more documentation for scalar example; added mathjax directives at multiple points
removed const keywords in scalar_sweeper; they should be there, no idea why it worked even with them
Merge branch 'pr/81/head' into release/v0.2.0

* pr/81/head:
  removed const keywords in scalar_sweeper; they should be there, no idea why it worked even with them
  more documentation for scalar example; added mathjax directives at multiple points
  improved docu for scalar example; added ** at several points
  extended documentation for scalar example

Signed-off-by: Torbjörn Klatt <t.klatt@fz-juelich.de>
examples: scalar: a few little cleanups

Signed-off-by: Torbjörn Klatt <t.klatt@fz-juelich.de>