Even spacing of DoFs for higher-order elements #250
Description
Until #238, the DoFs for higher-order Wtheta spaces were evenly spaced, rather than always including the cell edges -- e.g. using [0.25, 0.75] rather than [0, 1] for the reference element's nodal coordinates. Although this should be OK in theory, it threw up a number of issues for adopting a Wtheta-like space for the coordinate fields, as two neighbouring cells may then not agree on the coordinates of their shared face to the bit-level.
These problems were avoided by moving the nodal coordinates of higher-order Wtheta spaces in #238, but this may create issues for outputting fields in Wtheta when using higher-order elements.
This issue is intended to be a record of the problem.