Simulate alignment using the same name of observed data should be failed

[walterxie]

@data
Alignment codon1 = FilteredAlignment(data=alignment_data, filter="3-629\3");

...
@observed(data=codon1)
Alignment codon1 ~ TreeLikelihood(siteModel=siteModel1, tree=tree, branchRateModel=clockModel);

This should be illegal and throw exception.