update handbook for 3.2
Todo:
-
replace all mentioned versions to 3.2 -
change sentence to restart, add double precision restart for dune 2.7 -
add the new examples (freeflow and biomin?) -> remove list of examples and add link to git-repository -
update passage with backwards compatibility -
change all reference to dune 2.6 to dune 2.7
Edited by Katharina Heck