Checks the list of species code deifinitions supplied by the user
Firstly, it checks that there are not multiple definitions for the same species code. Secondly, it checks that the names of the ddf models correspond to the names in the species code definitions. Lastly, it checks that definitions are provided for all species codes and if not it adds the missing definitions assuming they correspond to identified categories
a list with an element for each unidentified code which contains a vector of corresponding identified species codes or NULL if not required
a vector of species names for which model names were supplied in the ddf.models list passed to execute.multi.analysis by the user.
updated species.code.definitions list
Internal function not intended to be called by user.