[common.header] do not disable -Wdeprecated-declarations
disable some warnings from core modules
[grid.provider.cube] default to a finer grid
move function -> functions
remove trailing whitespace autotools complained about
[grid.intersection] added missing include
also ReferenceElements does not exist in the current
dune-geometry release, replaced it by GenericReferenceElements
if it called ReferenceElements in the current master, we need a check
[lib] added math
[functions] fixed wrong includes
[test] fixed wrong function includes