osc: Add another scale option for forced windows.

If the OSC is rendered on a forced window (by --force-window), the scale can be configured with scaleForcedWindow.
osc: Display cache fill status

The OSC will now display cache fill status between the timecodes, but only if it's below 48% to not clutter the interface with erratically changing values.

By default, the displayed value is multiplied by 2 to not confuse users who are unfamillar with the inner workings of the caching system. This can be disabled using the iAmAProgrammer=true setting.