Clean up usage of doubles in Configuration spec

* Use an instance double of the Ruby logger as the logger double
* Use an instance double from our Connection
* Use real values for the other values, except the adapter
    * The adapter is an implementation detail of a dependency
Clean up usage of doubles in Connection Spec
Clean up usage of doubles in Cursor Spec
Clean up usage of doubles in Edge Spec
Clean up usage of doubles in index_spec

unique is a 'Boolean' double, because I don't want to test both cases
separately and there is no boolean type in Ruby :wink:
Collections, Part 1 (so many doubles oO)