Add per-project prolog submit rule files

When loading the prolog environment, now checks refs/meta/config
branch for a file called rules.pl. If it exists, consult the
file. Expects a predicate called submit_rule. If no file is found,
uses the default_submit predicate in common_rules.pl.

Change-Id: Ia76d0dc5aba67cf3c68c56589fe013c63157bca5
4 files changed