Bug 10699: add explicit return value for DeleteBranchTransferLimits()

Bug 10699: add explicit return value for DeleteBranchTransferLimits()

This patch adds return values to DeleteBranchTransferLimits:
1 if a Transfer Limit is deleted
undef if no parameters is given
0E0 if a wrong parameter is given

More, it fixes and adds some tests in t/db_dependent/Circulation_transfers.t

To test :
prove t/db_dependent/Circulation_transfers.t
t/db_dependent/Circulation_transfers.t .. ok
All tests successful.
Files=1, Tests=14, 19 wallclock secs ( 0.02 usr  0.01 sys +  0.39 cusr  0.02 csys =  0.44 CPU)
Result: PASS

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Tested with patch for bug 10692 applied.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>