-further improved the function for computing the likelihoods of trees
-it will now evaluate the likelihoods of all trees contained in the file passed via -t
-the operations are fully checkpointed
-one can chose between -f e and -f E
-the -f e option will do a fast tree evalutaion, just optimizing the likelihood model parames for the
 first tree in the file and the just optimizing branch lengths for all subsequent files
-the -f E option will re-optimize likelihood model parameters for each tree