It would be hard to implement on top of the latest feature and contradict
features projected for the near future.

fixes a nasty bug, where face information was omitted

By implementing repr such that instance addresses are
not part of sorting anymore

In ULF the jump is defined as jump(v) = v('+') - v('-'). Accordingly
the outer unit normal has positve restriction and ('+') refers to self
und ('-') to neighbor. Unfortunatly you can also find '+' and '-'
swapped in the literature.

The control operator doesn't accumulate in the residual. Instead the
localoperator has a member vector where the value of the derivative is
accumulated.

It does not yet do all the jobs it can do, but it exists and we can
run tests with it.

by introducing an order on the kernel objects and
using the first n kernels instead of an itertools.permutations
generator