H-matrix solving works. My work is done.

[tbenthompson]

Some notes on this:

• I changed the H matrices so that all the internal blocks are 2-dimensional instead of the old 4-dimensional internal matrices.
• I added the tranpose_dot function to HMatrix for when we need to do v @ A.
• You'll need to re-run the pickle.dump from celeri_hmatrix.ipynb.
• Then, hmat_dev.ipynb has the fun stuff!
• The main three challenges were getting the weighting right, setting up the column norm preconditioner and then getting the sparse matvec and rmatvec functions correct.

[tbenthompson]

(The notes are in the context of my discussion with Brendan earlier, sorry Jack if they don't make a ton of sense)