Unify cellular sheaf interface

[tylerhanks]

All types of cellular sheaves should implement the same interface.

I'm envisioning three main types of cellular sheaves:

1. Single threaded
2. Multi-threaded
3. Distributed (MPI)

Each of these types also probably need variants with edge potential functions.

The core functions that each of these types need to implement include

• Project a point to the nearest global section of the sheaf
• Apply the sheaf laplacian
• Apply the coboundary map

We should also implement conversions between the different types and adapt the cellular sheaf macro to be able to emit the different types.