Cleans up Config class's PHPDoc references.
Fixes class references for Config class

Several references to `\Phinx\Config\Config` have been updated from `\ArrayAccess`, which I presume is a vestigial reference.
Fixes incorrect and missing PHPDoc class references.
Removes unused use statements.
Updates PHPDoc with missing parameter types and @throws statements.
Fixes return types, PHPDoc input references

- a bunch of void methods weren't returning void.
- fixes a bunch of undefined variable errors.
- fixes PHPDoc statements to more specifically define array types.
- removes return statements on constructors.
Removes commented out variable assignments.
Merge pull request #236 from cyrusboadway/feature/code-cleanup

Code cleanup