Update for recent changes
Avoid exception when only 1 optimizer has errors in the test suite
Fix arguments of .DollarNames
Add mxFactor(..., collapse=TRUE)
Fix bug that failed to print optimizer messages again in summary. Add test.
Update ref models man page for behavior on using subsets of variables.
Fix mxEval(..., defvar.row) for when data is sorted
Spotted by Mike Neale. Simple test case provided by Mike Hunter.
Fix typo in error message
Check for duplicated level names in factors in MxData