`get_pkgbase` has been replaced with `get_pkg_or_base`, which is
quite similar, but it does take a new `cls` keyword argument which
is to be the model class which we search for via its `Name` column.
Additionally, this change fixes a bug in the `/packages/{name}` route
by supplying the Package object in question to the context and modifying
the template to use it instead of a hacky through-base workaround.
Examples:
pkgbase = get_pkg_or_base("some_pkgbase_name", PackageBase)
pkg = get_pkg_or_base("some_package_name", Package)
Signed-off-by: Kevin Morris <kevr@0cost.org>