Fix bug when loading duplicate instrument parameters.

The multimap was continuously growing as there was no way of checking
if a given parameter for a component was already loaded. The storage
is now a map with key <Component*,name> so that only unique
component/named pairs will be stored.
Refs #7743.
Fix case when no log exists for parameter link.

Also, improved error message for LoadEmptyInstrument
when running child algorithm.
Refs #7743
Add equality operator to ParameterMap...

and use it in CheckWorkspacesMatch. This avoids changes in ordering
within the map affecting whether the map is actually the same as another.
Refs #7743