Update issue #155 : Seeking - added toolbar buttons, menus, keyboard shortcuts for seeking backwards or forwards 1 frame, 1 second, 10 seconds, 1 minute
Frame seeking currently only enabled for graphs that support TIME_FORMAT_FRAME
Some filters cannot convert to and from frame time when the current format is media time - these usually work only if frame is selected as the time format in the seek dialog.

git-svn-id: http://graph-studio-next.googlecode.com/svn/trunk@257 c2f33eb2-41b2-391d-4cb4-d9d0608729ba