Add a `trigger` to args of an `:object.behavior.time` event.

I have exposed `trigger` on `:object.behavior.time` event as suggested on mailing list.
I was not sure how to go about `raise-reduce` cause I was not sure what the expected behaiov
is supposed to be:

- Is it supposed to return result of last application ?
- Does error in one of the behaviors supposed to break a loop and propagate errors ?