This patch basically adds all required parameters to play_rendered_anim() operator, allowing scripters playing back any rendered sequence or movie (according to the user preferences). Based on that work, I thought we can also provide a simple UI, which can be quite useful to review/playback the rendering without changing the current scene settings:
Personally, I never understood what the operator is doing under the hood and for that reason I always manually started an external player, I'm familiar with. However, I recently discovered the operator and I think it's actually a pretty nice feature if the user interaction would be better, so in addition to the popup I added some extra warnings and error messages as well, which should help users figuring out what's happening or what's might be wrong with the settings.
I'd appreciate any feedback.
Cheers,
Christian
Note: Successfully tested with all players except Framecycler (seems there is no standalone version anymore).
