Adding missing assignment to Xu_bdprob_cor@dependent_node_IDs in gen_single_bdprob.R

[langfob]

Added this line to gen_single_bdprob.R in commit fbb7a19 "Fix missing assignment to dependent_node_IDs (re: github issue #60)":

Xu_bdprob_cor@dependent_node_IDs               = PU_spp_pair_info@dependent_node_IDs    #  Added 2018 12 31 - BTL

The dependent_node_IDs slot already exists in the Xu problem class, but my tests today show that its value has never been getting set. That's because its value IS set in the PU_spp_pair_info object and then every time it's ever needed, it's either passed in to the function of interest or it's derived from the nodes object using get_dependent_node_IDs().

It looks like the slot is completely vestigial and unnecessary and should be removed, however, that would change the Xu problem class and might break reading any old copies of the class from disk.

So, I'm going to just set the value now and assume that it won't hurt anything because it's never referenced in the code. May want to remove the slot in the future.

[langfob]

Same problem exists in generating the wrap problem, so I've added a similar line there in
commit ad9cdd5 "Fix missing assignment to dependent_node_IDs in wrap (github issue #60 again)":

Had same problem in wrap as in commit fbb7a19 for gen_single_bdprob.R,
so I've made a similar change in wrap. Here though, the PU_spp_pair_info
structure didn't exist like it did for the other case, so I've just
assigned the value here to be the same value as in the base problem that
the wrap problem is wrapping, since that is the correct value by defn.

wrapped_bdprob@dependent_node_IDs                   = Xu_bdprob@dependent_node_IDs    #  Added 2019 01 01 - BTL