Energy-conserving EQP

[cval26]

I'm opening this draft PR so that you can stay up to date with my changes in the code, and so that I can ask you questions about specific parts of the code that I'm unsure of. I'll add comments to the parts of the code I have questions on.

I'll push new changes as I implement them so that we can discuss them. Once we have a correct implementation I can go back and edit the commit history so that it's easier to review.

The indentation in some parts of the code seems to be off in the diff files. I'm not sure why; it doesn't look like that in my editor.

Changes made so far:

• formed a new, combined NNLS problem for both velocity and energy;
• formed the new RHS force vectors used in the online timestepping phase;
• added the energy identity vector to each time window's reduced energy basis;