Remove BigMenu Logic

When BigMenu exists, NavBar assumes you want 'DONT_SHOW' for
left/right little menus.  This had spacing implications for users
that used BigMenu, but few buttons :
http://rootzwiki.com/topic/38274-menu-button-in-navbar/

removing this had little implication on the NavBar itself, but
did force some re-working of the MenuArrowKeys.

Change-Id: I6946d85d2e0a6db26b937a9ced9643c6a2a1ae83
Signed-off-by: Zaphod <mwilson@acesappraisal.com>