include votingMachine address in event GenericScheme.NewCallProposal

[jellegerbrandy]

On creating a new proposal, the schemeregistrar and contributionreward throw events that include a reference to the votingmachien address (these are the events NewSchemeProposal, RemoveSchemeProposal, NewContributionProposal)

The NewCallProposal event does not. This is inconsistent and slightly inconvenient.