Merge branch 'fix/parameters-include' into 'master'

[common] Fix missing include in parameters

See merge request !1987

(cherry picked from commit 2a9a2dfe)

9b4c2f53 [common] Fix missing include in parameters

dumux/common/parameters.hh

@@ -29,6 +29,7 @@
 #include <sstream>
 #include <unordered_map>
 #include <fstream>
+#include <functional>
 
 #include <dune/common/parametertree.hh>
 #include <dune/common/parametertreeparser.hh>