Popup menu for tabs
Delete unnecessary _reload method
Tab menu: added "Move to opposite panel"
Tab menu: set moved tab draggable
Tab menu: Added "duplicate tab" menu option
Main Window: set tab reorderable and derachible in _page_added
Main Window: Added method for get opposite notebook
Plugin Base: use new get_opposite_notebook method in _move_tab
Merge pull request #6 from ArseniyK/tabs

Popup menu for tabs