Replay button

[Raab70]

Here is my attempt at implementing a replay button (#295 and #318).

Through my testing this seems to be working. It is currently a hidden element in the toolbar, you need to patch, then right click on the toolbar and add it. I know someone had mentioned this in the bottom left, this was an easy way to get a working prototype and we can discuss ui placement.

Current issues:

1. The icon looks terrible, I'm not a graphics guy.
2. In Sources/AudioStreamer/AudioStreamer.m, I have to set the state to AS_PAUSED to get the play function to work although we're not technically paused. I'm not sure if this is really correct or a bad workaround. I looked at enqueueBuffer but that didn't look necessary.
3. I have not tested the menuItem functionality. The way I've been testing it still has the Xcode menu.

[raivivek]

Probably can be merged?