Bug 6825 OpacNav menu hide user menu on opac-user.pl page

Bug 6825 OpacNav menu hide user menu on opac-user.pl page

This patch add a new syspref OpacNavBottom which is placed on all pages
after OpacNav. On Patron pages, specif patron links are placed between
OpacNav and OpacNavBottom, like this:

  OpacNav
  Patron links
  OpacNavBottom

To test:

  1 Apply this patch
  2 For RM, modify kohaversion.pl and updatedatabase.pl appropriately
  3 Test that OPAC pages are displayed as before, OpacNav on the left
  4 Test OPAC patron pages: OpacNav is as before displayed after patron
    links
  5 Split OpacNav between itself and OpacNavBottom
  6 Patron pages display patron links between OpacNav and OpacNavBottom

Signed-off-by: Nicole C. Engard <nengard@bywatersolutions.com>
Signed-off-by: Ian Walls <ian.walls@bywatersolutions.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>