User localizable-bilinear-form.hh instead!

This can be used to compute the L^1 norm of a function, for instance.

* Upwind
* Lax Friedrichs
* Engquist Osher

* do not clear target DoFs, as advertised
* allow for non-scalar bochner functions

* update ListVectorArray usage
* add preliminary visualization

This

* adds a proper check of the template arguments, giving better static errors
* adds a local_discrete_function(element) method
* fixes make_const_discrete_function for Vector&&