Hardlines in `edgefx`

[krober10nd]

@Onur-Kurum adds the functionality to edit edgefx for better mesh sizing agreement around hardline constraints with variable point spacing in the mesh connectivity.

Potentially, meshgen will also need to process a cell-array or NaN-delimited array composed of several hardlines.

A hardline is a set of edges to-be-constrained in the mesh connectivity connected together by a set of fixed points. In OM parlance these are egfix and pfix kwargs.