Minor clarifications to self-tests code
Refactor selftest.runTests and create listTests

Not extensively tested.  Needs comments describing options to the new functions (e.g. getFilteredTests) and updated usage for `meteor self-test ––list`.

Filtering and running tests now proceeds in stages
- Add “pseudo-tags” like non-matching and unchanged
- Remove tests whose tags are in a list of “tags to skip”
- Run or list the resulting TestList
- Optionally report skipped tests
- Optionally save the testState
Improve output of `meteor self-test ––list`
Support ––file option to self-test
Take a ––file regex; comments and usage
Edit some comments
Show list of failed tests
Merge branch 'dgreensp-selftests' into 0.9.4

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