Closes CompEvol/BeastFX#105

[Lars-B]

No description provided.

[Lars-B]

Actually, I just found that there is a UserTargetTreeTopologyService class.
The correct call should be treeannotator -target file.tree -topology target ... which does the trick.

So a cleaner fix will be to set topology to target if the user passes a -target argument.

[Lars-B]

Now passing -target file.tree does the same as -topology target -target file.tree by assuming that the option -target always implies -topology target which seems reasonable. #105