Mimetic Spectral Elements

[celdred]

This pull request adds mimetic spectral elements (described at https://www.sciencedirect.com/science/article/pii/S0021999113006414 and https://arxiv.org/abs/1111.4304), both the primal and dual complexes. This is done by adding the relevant 1D H1 element for the dual complex: Extended Gauss Legendre (EGL); and the L2 edge elements associated with GLL and EGL. These are non-Ciarlet finite elements that use a basis that histopolates (http://people.math.sfu.ca/~nrobidou/public_html/prints/histogram/histogram.pdf) rather than interpolates. The nD deRham complex on hypercubes is then accessible using the variant keyword (either “mse” or “dualmse”) with the relevant elements (DQ, Q, RTCF, etc.).

[miklos1]

Okay, so this pull request is not very useful here. FIAT and UFL pull requests should be filed against upstream to be merged: https://bitbucket.org/fenics-project/fiat

If you want to receive code review from the Firedrake team before filing the pull request upstream, then please file the pull request against firedrakeproject:master and not FEniCS:master (as is the case with this PR). Since this GitHub mirror is quite out of date, the diff shown for this PR is practically unreadable.

[wence-]

Rebased onto master now that this is where things are happening.

[miklos1]

Updated this with master.