rules.enable: Support disabling project rules

The rules.enable variable can be set to false in gerrit.config,
allowing a site administrator to globally disable execution of
the per-project Prolog rules.

Change-Id: Ie15cbea9c9dbc386ff75c8ab08c30474d8f717aa
Signed-off-by: Shawn O. Pearce <sop@google.com>
2 files changed