TimingFramework triggers for Trident

[<remy.rakic@gmail.com>]

Hey Kirill, 

I was just testing Trident the other day, and thought the trigger
feature from the TimingFramework would be interesting to have (In case
you're not familiar with it, it's basically a way to start and reverse
an animation when specific events occur, ie it's a nice high level
concept that adds listeners for you - kinda neat). So i "ported" them
to Trident.

It's not deeply tested, and moreover i have close to zero experience
with either library :) That being said, i eyeballed that the triggers
included in this.

You can find it here, i also added a modified ButtonFg demo, that
exercises most, if not all, of the included triggers. (I also added 

I decided not to port the animation triggers (trigger on an animation's
start and stop events), because from my limited understanding of both
libraries, this feature seems to be supported in Trident with
TimelineScenarios, and parallel and sequential animations is what i
think those triggers were meant to help achieve.

Let me know what you think.

ps: Developing this, i think i got bitten by this: is the timeline
state change totally asynchronous and in another thread ? in my first
trials i suspended, played, resumed in a sequence quite fast, and at
some point i thought the state was not the one i was expecting. Is
there a way to get state changes from a timeline other than adding a
callback to it os is this the preferred way to go ?