Use DatabaseConfigurationProvider to get DB info

Summary:
remove accessing the db config info directly. Use
DatabaseConfigurationProvider instead. Also fixed a minor issue where
different number of newlines are output in PhabricatorSetup.php's output.

Test Plan:
executed upgrade_schema.php; executed PhabricatorSetup.php by
setting 'phabricator.setup' to true.

Reviewed By: epriestley
Reviewers: epriestley
CC: aran, jungejason, epriestley
Differential Revision: 443