Harmonize mode participation factor output with MSC

[victorkemp]

Make them compatible. They're currently:

Mystran

MEFFMASS case control command

• modal effective mass
• modal effective mass fractions?

MPFACTOR case control command

• modal participation factors

MSC

MEFFMASS case control command

• modal participation factors
• modal effective mass
• modal effective mass fractions

PFMODE case control command

• modal participation factors

Siemens

MEFFMASS case control command

• modal participation factors
• modal effective mass
• modal effective mass fractions