+ Added EffectMapping with one-shot and batched variants.
+ Added EffectHandler type and Effect node to the query algebra.
+ Added EffectElaborator phase which maps selections of effect-mapped
  fields into Effect nodes.
+ Generalized StagedJson to EffectJson, handling both components and
  batched effects.
+ Simplified effect/stage grouping/batching logic.
+ Renamed and simplified Mapping#combineQueries to combineAndRun. This
  also replace QueryInterpreter#runRootValues which has been removed.
+ Several root APIs (eg. defaultRootCursor) which were previously
  parameterized with a Type and/or an Env are now parameterized with an
  optional parent Cursor. This allows for more uniform inheritance of
  runtime attributes between components.
+ Removed redundant Defer node from the query algebra.
+ Reordered the argument to the component join for consistency.

+ Renamed EffectMapping to EffectField.
+ Added scaladoc for PossiblyRenamedSelect.
+ Added sqlCursor method similar to circeCursor, valueCursor etc.
+ Extended test to illustrate making a follow on SQL query driven by
  values returned from an intermediate service request.