Big update of the mouse events and fix of the context menu on the Linux.
- Because in the Linux context menu usually opening on mousePress event, the mouseReleae event doesn't work. This update set opening of the item's context menus only after mouseRelease events.
- Added protectors, which disable possibles for make bugs with moving items if you press multiple mouse buttons.
- Context menu will not be opened on right mouse button switching from editing mode into selecting.

Later same update will be applied for World Map with same organizing which made in the level editing workspace.