Added OVVReady event; VPAID AdVideoStart starts interval

This allows the ad to wait for all beacons to load before dispatching the AdLoaded event to the player, so they are not loading while the video is playing.
Updated comment
Fixed potential race condition
Added AdVideoStart to list of VPAID events which have listeners
Added a comment
Stop polling interval once impression or unmeasurable event has been dispatched.

Polling the beacons adds can affect video performance and is unnecessary once the ad has been determined to be viewable or unmeasurable.
Don't bother polling the control beacon
Formatting
Make geometry aysnc so beacon and geometry methods behave the same for the ad.
Provide ready state to ad.
isJsReady is a getter.
Leave interval check running for log events
Merge branch 'master' into readyEvent-IntervalOnAdVideoStart

Conflicts:
	src/org/openvv/OVVAsset.as
	src/org/openvv/js/OVVAsset.js
Leave interval check running for log events
Added OVVReady to OVV_EVENTS array.
Changed interval start trigger from AdVideoStarted to AdImpression; renamed videoStarted to adStarted
Merge pull request #66 from openvv/readyEvent-IntervalOnAdVideoStart

Ready event added; interval starts on adImpression