Utility method that overrides the standard `$' list accessor to disable
partial matching for ergm control.list objects
# S3 method for control.list
$(object, name)Returns the named list element exactly matching name, or
NULL if no matching elements found
list-coearceable object with elements to be searched
literal character name of list element to search for and return
Pavel N. Krivitsky
Executes getElement instead of $ so
that element names must match exactly to be returned and partially matching
names will not return the wrong object.
see getElement