Cosmetic changes to test summary.
Make setUp() and tearDown() more robust.

In MiniTest's setUp() and tearDown(), ignore a raised error
only if it caused by a missing setUp() or tearDown() in the parent.
Replace 'as string' with 'as text'.
Cosmetic changes to the output.
Set name property in MiniTest scripts.
More cosmetic changes to the output.
Add more comments.
Turn test runners into test loggers.

Remove the responsibility of running the tests from TextTestRunner,
that is, make TextTestRunner just a logger of the results collected by
TestResult. Instead, use an autorun() handler to set up the required objects
and to execute the tests.

Given the recently introduced ability of adding more than one observer of
a TestResult object, we are now ready to implement different loggers, and
possibly running more than one logger at a time.
Reorganize the code. Un-nest MiniTest.
Fix tests.
Refactor loggers. Add ConsoleLogger script.
Rename Logger -> TestLogger.
Improve console output.