* IMPROVED:  `mxFitFunctionMultigroup` help. Made clear what the function expects as input; Expanded description; Documented example; Added an mxCompare to make sense of what a multi-group model does.
* IMPROVED:  `mxFitFunctionMultigroup` help. Made clear what the function expects as input; Expanded description; Documented example; Added an mxCompare to make sense of what a multi-group model does.

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