Clean up DirectSqlStore implementation

* Order all class properties:
  * Constructor parameters first,
  * then all other properties set in the constructor,
  * then the rest in unchanged order.
* Inline trivial new...() methods.
* More meaningful variable names.

Change-Id: Id046892c9872ff5b5761d4221fa2c59dac3efc9d
Merge "Clean up DirectSqlStore implementation"