Add Lagrange function with bubble on cubes

The MR adds a new local finite element that represents a multi-linear basis function on cube elements enriched by a single bubble function. The bubble function is a quadratic polynomial that vanishes on all facets of the element. This can be constructed as product quadratic edge functions (the product of the two vertex functions)

added feature label

This is ready from my side.

requested review from @carsten.graeser

assigned to @simon.praetorius