Fast evaluation of jacobian of the err:
   Model3 now caches operators H1 H2 KE
   Model3 cache evaluation takes advantage of situations where only 1 mixer changes
   Fitme.errJac is new function that uses Model3 for Jacobian evaluation
   Fitme.err implementation of parallel algorithm fundamentally changed
         change in parallel approach was due to file read/write becoming rate limiting
   parallelHF is new global function called by Fitme.err