Tabs and fix for splitpanes being reset during resize

[Bl3nd]

• Renamed CloseButtonComponent to a more suitable name: TabComponent
• Cleaned up DraggableTabbedPane
• When closing a tab using "Close All but This" or "Close Tab" in the context menu, it would not remove the tab from the openedTabs array, so when trying to open up the closed files it would not let you.