Add service inheritance sugar
Support inheriting services in parameterized containers
Make the container sugar add subcontainers even without a block
Simplify the container sugar
Implement container inheritance
Simplify the container sugar further

There was only one place branching on $name_is_obj left, so we might as well get
rid of the temporary.
Containers owned by other containers aren't subcontainers
Test subcontainer inheritance
Base registering subcontainers on $is_inheriting, not has_parent
Merge pull request #27 from rafl/container-inheritance

Implement container inheritance