Add MUSCL Reconstruction

[wilfonba]

Tracking item for MUSCL addition.

[wilfonba]

Steps to add MUSCL to MFC

• [x] Implement MUSCL
• [x] Validate against quasi-1D Sod Shock tube
• [x] Validate against 2D advection problem
• [ ] Validate against 2D shock-droplet
• [ ] Validate against 3D spherical-bubble collapse
• [ ] Ensure viscous effects work as expected (shear layer)
• [ ] Ensure sub-grid bubbles work as expected (bubble screen)
• [ ] Ensure hypoelasticity works as expected (unsure)
• [ ] Compare run time on GPUs to WENO

[sbryngelson]

@wilfonba would be nice to add this if possible. some cases may only run with MUSCL...

[wilfonba]

I'll add this back near the top of my list. I'd honestly forgotten about it.

[sbryngelson]

No worries. Get to it as you can... though I would like to leave it as a to-do because it is genuinely useful.