Implements master ignore list

Implements master ignore list

This change introduces a master ignore list, to save having
to repeat ignore strings in every project exception file.

This is achieved via a new ignore_list.yaml file that is
merged with the project exception list and then used for the
re.search ignore statement in both patch_scan.py and
project_scan.py

Change-Id: Ifb60b8ba3091603182c2025dbbbfd1a88a72439b
Signed-off-by: lhinds <lhinds@redhat.com>