change(git-update): use SQLAlchemy ORM and pytest

In addition, some changes were made to aurweb.testing.git
and testing/templates/{PKGBUILD,SRCINFO}.j2 to make testing
a bit easier with the utility.

- removed t1300-git-update.t sharness test
- fixed SRCINFO.j2, PKGBUILD.j2

Signed-off-by: Kevin Morris <kevr@0cost.org>