Issue #287 Remove the match capture
Remove paren in the output string
Clean up logline_decoder captures

- Fail MatchRegex configurations with no capture groups
- Remove the Submatch/SubexpNames bounds check
Remove additional references to the match captures

- Update the lua and plugin docs
- Correct the output plugin format string
Merge pull request #288 from mozilla-services/issue_287

Issue #287 Remove the match capture