Move the "Show Included In" menu item

Move the "Show Included In" menu item

The "Show Included In" context menu was grouped as part of the
view-specific actions (setting width, height, orientation,
etc). That's not really a good place since this option is really about
the view as a whole. This changeset moves the item down to the bottom
of the context menu, next to the "Show In" action (which lets you show
the content in another Eclipse view.)

The code was tweaked a bit to be computed lazily (e.g. the contents of
the include list is not computed until the actual Show Included menu
is opened.)

Change-Id: Ic18997271e9ffde491a1a63e337ff015d762a20a