Updates to the Classic mode histogram

[gundamftw]

• Corrected the "Classic" mode histogram. Now it shows an actual wave form instead of unreadable garbage. Also moved the graph to the top of the frame.
• Added a "histonly" option to Classic mode to show histogram only. Default to off.

The corrected wave form is created by turnright -> draw classic histogram -> turnleft. So the code is basically doing this:

clip = core.std.Transpose(clip)
clip = core.std.FlipHorizontal(clip)
clip = core.hist.Classic(clip)
clip = core.std.FlipHorizontal(clip)
clip = core.std.Transpose(clip)