Small fixes (#155)

* Fix various typos and references or links

- Misuse of product macro the x sign did not appear
- Use macro for milligrams
- Some refes were without hyperlink for some reason ?
- confusion between section and subsections
- a little grammar.. exact value not absolute, don't think a negative
  amount of flower was ever an option :D

* Use siunitx for temperature everywhere

Apparently some files escaped my script last time, or messed up in git
merge... Anyway fixed now and should be more consistent.

* Simplify Fermentolysis table

I woudl hope this is more clear with less lines.

* Remove double bottomrule

* Fix grammar

* Use correct font familly in preface

Small corrections on font familly and extra space for signature.
TODO: I did not change the paragraph breaking but we might want to
revisit it later.

* Fix wrong percentage range

fixes https://github.com/hendricius/the-sourdough-framework/issues/156

book/sourdough-starter/sourdough-starter.tex

@@ -60,8 +60,8 @@ we have \qty{1.4}{\kg} at hand (\qty{1400}{\gram}).
 For each ingredient we calculate the percentage
 based on the flour available (\qty{1400}{\gram}). So for the water
 we calculate \qty{60}{\percent} based on \num{1400}. Open up your
-calculator and type in \numproduct{1400}{0.6} and you have
-the absolute value in gram  that you should be using.
+calculator and type in \numproduct{1400 x 0.6} and you have
+the exact value in grams that you should be using.
 For the second day, that is \qty{840}{\gram}. Proceed to do the same
 thing for all the other ingredients and you will know
 your recipe.