Utility method that overrides the standard `$' list accessor to disable
partial matching for ergm control.list objects
# S3 method for control.list
$(object, name)list-coearceable object with elements to be searched
literal character name of list element to search for and return
Returns the named list element exactly matching name, or
NULL if no matching elements found
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