Move code of file tab into separate class FileTab.
Add menu item to split panel horizontally or vertically.
Start from single panel in the main window and split it on demand.
Fix splitting of left component.
Close panel
Create common superclass AnimationPanel for graphics panels.
Unregister panels from SimulationAnimation upon closing.
Set particle panel as default panel when splitting panels.
Show "close panel" menu item only for components in JSplitPane.
Replace panel also at top level.
Clean up code, extract method.
Merge pull request #84 from aipp/graphicspanel

Split panels horizontally or vertically