Unset subviews' parent before converting tabview to a splitview.
Add names to panels.
IDEAppController should know which tabview is currently active.
Set editorPane as default activeTabView.
Added helper methods to split and merge editor area.
convertToSplitView method accepts an argument for created split view's type.
Set parent and splitView options to created split view panels.
Added mergeSplitView method.

Test needed.