Mike Kelly authored Nov 19, 2013 and Robert Lyon committed Jan 06, 2014

Bug #1266317

Group pages, site and institution pages were set as having usr = 0 in
usr_custom_layout because the view owner is null.

Fix by adding group column to table, foreign keyed to group table.

usr column and group column have to be changed to allow null values, and
to have null as default values.

When saving a custom layout, check context, then set usr and group
values accordingly. 
e.g. 
usr = 5, group = null 
usr = null, group = 321
In the case of site and institution pages:
usr = null, group = null

Change-Id: Id42ebcc543d29ee2455aef73227b57c569171385
Signed-off-by: Mike Kelly <m.f.kelly@arts.ac.uk>