Provide two separate constructors instead.

Conflicts:
	dune/fufem/assemblers/localassemblers/subgridl2functionalassembler.hh

And with it the quadorder member.

Additionally slightly improve code readability.

The BaseType functions are VirtualFunctions exhibiting
const methods only anyway, so it should accept const
BaseType functions directly.
Otherwise explicit and unneccessary const_cast is needed
when SumFunctions are used.

Without this change, the default settings invoke libtool with --tag=CC,
which leads to link failure

the dune-solvers transferoperators, i.e. from the coarse basis
to the fine.

one basis that is contained by the other one

one basis into another living on the same gridview

make default implementation work for diagonal transformation matrices; there are no performance drops for dense matrices due to the change (tested)

to make the adouble operations avaiable to other Dune
classes when the adouble type is used.