removing pipeline from api

The ceilometer API server allows new samples to be posted via the
API. These are then processed through the pipeline and then
dispatched as required. This means the API server must use the
pipeline code and have a ``pipeline.yaml`` file, raising the
complexity of the code and the testing and install profile of the API.
An alternative would be for the API server to publish notifications
for the meters it receives which would then be processed by the
notification agent (which has a pipeline of its own) and then
dispatched.

Including the transformation pipeline in the API server increases
complexity on at least three dimensions for a single feature in the
API (creating samples) which is not commonly used (most samples are
produced via polling agents and notifications).

The use of the pipeline creates dependencies in code, testing and
installation that could be avoided. In code we must include the
pipeline modules and classes. In testing and installation we must
have a ``pipeline.yaml``.

In the installation case, if there are multiple API servers, the
``pipeline.yaml`` must be kept in sync across the hosts on which
those servers are installed. That's an unnecessary burden.