Add function to reverse play videos (step frame by frame backwards)

[curtishall]

http://community.bluecherrydvr.com/topic/client-2-2-2-issues

[jasauders]

If I may, does this issue have to be limited to focusing on stepping frames backwards only? Reason I ask is I had a downloaded video (continual record, 15 minute segment) that I was trying to catch something. This particular player can step forward and backward in either 5 second or 60 second increments (left -5 seconds, right +5 seconds, up +60 seconds, down -60 seconds). I found this combination very efficient to locate the event in question. Just my 0.02, but as an end user, that was very nice, and might compliment the client nicely.