CMS-3636 LiveEdit - Use ContextMenu from api.ui.menu instead of LiveEdit.ui.contextmenu.ContextMenu

- deleted live edit's context menu
- updated api context menu and styles
- added api context menu with title
- created .arrow mixin for generating css arrows for tooltip and context menu
- renamed ContextMenuWithTitle to ItemViewContextMenu
- changed context menu creation from config to static items in every item view