Allow parameter patterns, generalization of parameter types

[ilyash-b]

Related: #78

Now:

        F on_event(chc:ChannelHandlerContext, ev:ChannelEvent) {
            guard ev == ChannelEvent::active
            log("active")
        }

Should be:

        F on_event(chc:ChannelHandlerContext, ev:ChannelEvent::active) {
            log("active")
        }

Note that ChannelEvent::active is an instance, not a type

[ilyash-b]

Already done