Changeset 904 in tests for trunk/tests/db.php

Rename tests to conform to this standard: the class Tests_A_B_C.php should be found in Tests/A/B/C.php.

One class per file. Tests are now organized by general component, rather than by the core file they are found in.

Work in progress. Some classes need to be renamed, and some files still need to be moved (and split up).