Use re-sizable pane and allow a horizontal paperstrip

[xyzzy42]

This lets the pane between the paperstrip and waveforms be resized. If one is currently more interested in one of the other.

Also adds a menu and config file option to re-arrange the widgets so that the paperstrip is drawn horizontally instead of vertically. This allows much more space, and time, for the paperstrip, which is often much more useful than the waveforms. The layout can be changed while running.

See commits for much more detail on the changes.

Example of maximizing the paperstrip in vertical layout:

Example of the horizontal paperstrip. The time show in the strip is almost double what the vertical strip fits.

[jpolton]

I really like this functionality. I compiled and ran it on OSX10.15 (Catalina).