Protein and DNA settings do not get updated in GUI

[smirarab]

In GUI, if you choose a Protein dataset, and then select to a DNA dataset, when the DNA alignment is read, the datatype and models are not updated to DNA.

The reason is the following line:

                     if self.datatype.Value == "Protein":
                         datatype_list = ["PROTEIN"]
                     else:
                         datatype_list = ["DNA", "RNA", "PROTEIN"]

So, when the data type is set to protein, automatic type selection is not given the option to choose other types.

Not sure why this if is needed, but it seems really weird that if you mistakenly select a protein alignment and then switch to a dna alignment, the GUI gets confused.