SimpleTest conversion

Overview

The migration is pretty straightforward:

1. create new test file in `xxx/tests/yyy_test.php`
2. copy contents of the old test file
3. replace extends UnitTestCase with extends basic_testcase and extends UnitTestCaseUsingDatabase with extends advanced_testcase
4. move constructor code to setUp
5. fix setUp(), tearDown()
6. fix assert syntax
7. add $this->resetAfterTest() in advanced test cases that modify database
8. add missing global $CFG for includes outside of testcase classes