Weakagree and Alive claims now also allow for a role parameter + BUGFIX.

Previously, weak agreement and aliveness claims would enforce a requirement for all agents in the range
of the rho of the claim run.

For some three-party protocols this was stronger than needed. We now allow an
optional role name parameter for these claims; if such a parameter is used, the claim
is only evaluated for the agents performing that role.

En passant fixed a potential bug: aliveness and weak agreement require a run for each
agent, but previously we didn't check if these were helper protocols. Clearly they
should not be.