modify FaultSectionPrefData

[Ned Field]

I modified FaultSectionPrefData? to: 1) contain a coupling coefficient; 2) add option to apply this and aseismicity factor to various get methods (e.g., getOrigSlipRate() versus getReducedSlipRate(); 3) apply aseismicity as an increase of upper seismogenic depth only (no change in lower seismogenic depth) as recommended by Ray Weldon; and 4) cache the Stirling surface for efficient distance calculations.

I moved the previous getSimpleFaultData(aseisReducesArea) method to getSimpleFaultDataOld(aseisReducesArea), where the latter applies aseismicity as a modification of both upper and lower seismogenic depths (needed for UCERF2 and other legacy calcs). I used my judgement in what should apply the new method, so be on the lookout for potential problems.