Update FAH packaging

[jchodera]

This change updates the FAH packaging scripts to

• Ensure PME parameters are set explicitly. Addresses https://github.com/pandegroup/openmm/issues/1108, https://github.com/FoldingAtHome/openmm-core/issues/64, https://github.com/FoldingAtHome/openmm-core/issues/67
• Ensure MonteCarloBarostat temperature is the same as specified temperature for integrator

[jchodera]

Can you review when you get a chance, @danielparton?

[danielparton]

Looks good to me