Bug 5390: OPAC loses library selection

Bug 5390: OPAC loses library selection

This patch ensures that the OPAC library selection masthead will always default
to the branch that is currently being searched. This only applies to systems
with multiple branches and OpacAddMastheadLibraryPulldown turned on.

To test: do a search in the OPAC, limiting by branch. The search results will
still have that branch selected in the masthead dropdown.

This patch also fixes bug 5852 and bug 3778.

Signed-off-by: Ian Walls <ian.walls@bywatersolutions.com>
Signed-off-by: Liz Rea <lrea@nekls.org>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>