Fixes #3805, reverted change in log importer that looked for end-of-line after format regex match and modified format autodetection logic to pick the format based on whether the format matches and the number of groups returned in the match.

Notes:
  * Added several more tests to log importer tests.py. Added tests for checking format of log files w/ extra junk info on log lines. Added individual tests for parsing regex format.
  * Modified log files used in ImportLogs test, added extra junk info to end of some lines.
  * Fixed failing test in tests.py for the S3 log file format.