[Flash object] Add ability to flash color tint, object effect, and opacity (fade) (#955)

* Updating Flash extension (thanks Entropy!)
- Replaces deprecated functions
- Added "seconds" time unit to parameters
- Added FlashColor, FlashEffect, and FlashOpacity behaviors
- When "Flash object" action is used during a pre-existing flash, simply extend the duration of the flashing
 - Previously, it always performed "hide object", potentially causing the object to be hidden too much

Author: tristanbob