implement /packages/{name} as its own route

A few things added with this commit:

- aurweb.packages.util
    - A module providing package and pkgbase helpers.
- aurweb.template.register_filter
    - A decorator that can be used to register a filter:
      @register_filter("some_filter") def f(): pass

Additionally, template partials have been split off a bit
differently. Changes:

- /packages/{name} is defined in packages/show.html.
- partials/packages/package_actions.html is now
  partials/packages/actions.html.
- partials/packages/details.html has been added.
- partials/packages/comments.html has been added.
- partials/packages/comment.html has been added.
- models.dependency_type additions: name and id constants.
- models.relation_type additions: name and id constants.
- models.official_provider additions: base official url constant.

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

test/test_package_dependency.py

@@ -77,6 +77,13 @@ def test_package_dependencies():
     assert pkgdep in optdepends.package_dependencies
     assert pkgdep in package.package_dependencies
 
+    assert not pkgdep.is_package()
+
+    base = create(PackageBase, Name=pkgdep.DepName, Maintainer=user)
+    create(Package, PackageBase=base, Name=pkgdep.DepName)
+
+    assert pkgdep.is_package()
+
 
 def test_package_dependencies_null_package_raises_exception():
     from aurweb.db import session