Feature/fsisphInterfaces

[jmpearl]

Summary

• NOTE : this PR breaks backwards compatibility for the FSISPH package. Constructor arguments have changed.

This PR updates the following in the FSISPH solver:

• Interface fieldLists have been updated to be more robust and add functionality. A new fieldlist is introduced to FSISPH "interfaceAreaVector" which allows pressure boundaries to be applied to free surfaces. "interfaceFlags" are added to more robustly identify material interfaces and free surfaces.
• To control tensile instability, XSPH is updated to only be applied in regions where negative pressure exist.
• Decoupling logic is updated to account for recent changes in spheral's strength and damage models
• The option to evolve the deviatoric stress in plane-strain mode is added for 2d/1d simulations
• User can now specify an "interfacePmin" which sets the minimum pressure across material interfaces
• pressure/rawPressure switched to damagedPressure/pressure, this fixes a bug related to what pressure is fed in to the calculation of strain for the damage model. The new names are more clear as well.

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ToDo :

• Annotate RELEASE_NOTES.md with notable changes.
• Create LLNLSpheral PR pointing at this branch. (PR#)
• LLNLSpheral PR has passed all tests.

[jmikeowen]

Looks good to me