ZF-6428: authenticate() always fails on IBMi when using DB table-based
authentication.

Ensure that a lowercased zend_auth_credential_match element exists in
$resultIdentities array when the array is created.
Add Unit Tests specific to IBMi DB2 for CredentialTreatmentAdapter
logic.
Add TestConfiguration constants to control the unit tests.
Merge branch 'fix-6428' of https://github.com/clarkphp/zf2 into fix-6428
Correct a PSR-2 Code Style error I had missed before issuing PR.
Reword a few comments.
Format source code to better conform to ZF2 Coding Standards:
https://zf2-docs.readthedocs.org/en/latest/ref/coding.standard.html
Merge pull request #6510 from clarkphp/fix-6428

Fix 6428 - authenticate() always fails on IBMi when using DB table-based authentication
[#6510] Fix test setup

- Moved declaration of driver options into `setUp()` so that we can know
  constants are declared before we attempt to assign their values.
Merge branch 'hotfix/6510'

Close #6510
Ignore some files/paths when running CS checks

- Recent changes to php-cs-fixer (see
  https://github.com/fabpot/PHP-CS-Fixer/issues/422) have led to errors being
  raised that should not. This change to the php-cs-fixer configuration places
  several new paths into the "do not test" list. They will be re-instated when
  the issues are fixed.
Merge branch 'hotfix/cs-overzealousness'

Fixes #6520
AbstractAdapter::getItem() should return null, when the item cannot be retrieved.