Make default pane indicator internal
Make default pane indicator internal

No need to expose this.  There's a lot of copy/paste between
implementations of IPaneIndicator, this should be refactored at some
point.

elnomade/dockpanelsuite,15070217668/dockpanelsuite,joelbyren/dockpanelsuite,15070217668/dockpanelsuite,rohitlodha/dockpanelsuite,ArsenShnurkov/dockpanelsuite,xo-energy/dockpanelsuite,angelapper/dockpanelsuite,thijse/dockpanelsuite,dockpanelsuite/dockpanelsuite,Romout/dockpanelsuite,compborg/dockpanelsuite,RadarNyan/dockpanelsuite,jorik041/dockpanelsuite,transistor1/dockpanelsuite,shintadono/dockpanelsuite