(NC-133) Synchronize class definitions from puppet

This adds the ability to retrieve class definitions from puppet and merge them
with the internal definitions. A new endpoint at /v1/update-classes accepts a
POST request with no body to trigger this.

This depends on features in Puppet 3.5, which is unreleased. In order to test
this, the integration test code now allows installing development builds of
puppet.
(NC-133) Add integration test for multiple updates to puppet class definitions
(NC-133) Correctly handle re-creating classes and parameters

We didn't handle the case of calling a create function on a class or parameter
that was deleted by setting the deleted field. This fixes that.