Routing context is a map of string key-value pairs. It is send to the
database when calling `dbms.cluster.routing.getRoutingTable` procedure
as it's single argument. This is only supported by 3.2+ servers.
Previously routing context was defined on the config. It is problematic
because routing context in `bolt+routing` specific and thus makes no
sense for single instance database.
This commit makes routing context part of the `bolt+routing` URI. It
lives in the query part of the URI as regular query parameters like:
`bolt+routing://localhost:7687/?policy=my_policy&region=china`.
Clustering-specific configuration method is removed.