added if statement for subsets that cause an error for site likelihood calc

* For some reason some subsets are analyzable by the -f B but not -f g
calculation. If something goes wrong in the -f g calculation, we get a
"1" back from kmeans_split_subsets, the subset is marked as
"fabricated" and we move to the next.
added try/except for PhylogenyProgramError in site likelihood calc

* There are instances where the subset can be analyzed by the -f B
option in raxml, but not the -f g option. This finds those exceptions,
marks the subset as fabricated and returns a 1 to move the algorithm
along.
* So far the only error that escapes the -f B but is brought up during
site likelihood calculation is taxa consisting of entirely undetermined
values, so that is all that we except right now.