tools/qa-checks: Add git commit_msg_check module

This patch adds the commit_msg_check module that checks that the latest commit
of the repository has a commit message that complies with the repository
standard.

Issue-Id: SCM-2584
Signed-off-by: Richard Neill <richard.neill@arm.com>
Change-Id: Ib8ea2c88777522db25e8c5cfcc8547739632fea8