CIF to CIF Remove requirements removes too much information.

Consider the following specification:

input bool X;
event c_on;

requirement p:
  plant invariant c_on needs X;
  location:
    initial;

end

Removing requirements results in:

input bool X;
event c_on;

Notice that the plant invariant is also removed. This should not happen.

We should add as a restriction that requirement automata may not contain kindless, plant, or supervisor invariants.

Alternatively, we could move the non-requirement invariants outside of locations to the parent group/specification. Location invariants can never be supported as the locations are removed and we cannot refer to them.