Allow renewal limits to be overridden

Allow renewal limits to be overridden

Originally by Jesse Weaver <jesse.weaver@liblime.com>

This patch creates a new system preference, AllowRenewalLimitOverride,
that, if YES, allows the renewal limit to be manually overridden. It
updates C4::Circulation and reserve/renewscript.pl to obey this.

Adapted for 3.0 : Henri-Damien LAURENT
Signed-off-by: Galen Charlton <galen.charlton@liblime.com>
Signed-off-by: Henri-Damien LAURENT <henridamien.laurent@biblibre.com>