[wip] added some point-wise convenience functions for FemTools

This isn't ready to merge yet, but it is needed for @ahmadia's gauges. 
- onElement test for ReferencElement objects
- pointwise getInverseMap for ElementMaps objects
- fixed some bugs in MultilevelProjections

We probably need to split the extensions to FemTools from the  multigrid changes. I did get the multilevel solvers updated so that they run in serial,  but I decided  to take a more direct  route to the supporting the gauge interpolation.
Shouldn't this raise a NotImplementedError if it hasn't been defined yet?