Remove global vars; augment basic-handler for auth
Remove global vars; augment basic-handler for auth

Using special variables for host and port was viable, but now we're
tracking protocol (HTTP vs HTTPS), plus username and password for
authenticating to the Neo4J server.

- augment the basic-handler class with fields and methods for those
  attributes
- tweak 'format-neo4j-query to take an optional :protocol arg
- alter 'def-neo4j-fun to take a :request-handler arg, which is assumed
  to be of the 'basic-handler class, and to perform basic authentication
  to the Neo4J server.
- remove 'with-neo4j-database and 'with-request-handler, because they're
  redundant now that a handler object needs to be explicitly passed in.

equill/cl-neo4j