Fix launcher not propagating debuggee exit code.
Fix attach-by-PID without explicit --log-dir overriding PTVSD_LOG_DIR (and disabling logging).
Improve test logging, with a separate directory for every test.
Various test fixes.
Move docstrings to top-level package, and update them to reflect the current behavior.
Remove unused code in ptvsd.common.log.
Move sys.path/prefix/site_packages logging into ptvsd.common.log, and log it from adapter and server to the same level of detail as the tests.
Fix injected code snipped for attach-by-PID.
Fix some Unicode issues in adapter and tests.
Refactor Timeline, debug.Session, and start methods.
Wait on a breakpoint before checking output.
Add temp workaround for #1574: Flask tests fail with "no such option: --wait" on windows py27
Pin Flask version to last known good one in tests/requirements.txt.
Other fixes and improvements:
Make start_method mandatory for debug.Session to avoid problems with tests forgetting to specify it.
Add debug_me.scratchpad to enable async communication between test code and debuggee.
Improve debug.Session logging.
Improve test_attach.
Fix Flask and Django multiprocess tests.
Fix test logs not being captured by pytest.
Fix "import debug_me" check improperly applied in tests where it is unnecessary.
Fix some clarifying patterns not respecting the underlying pattern.
Add pattern helpers for strings: starting_with, ending_with, containing.
Move DAP test helpers to a separate module, and add a helper for frames.
Add support for line markers when setting breakpoints and matching frames.
Assorted test fixes around handling of Unicode and paths.
