Bouncerscript

Added
- Support for thunderbird scope prefixes.
- Support for `*-ssl` prefixes for thunderbird.
- Support for `thunderbird-next-*` prefixes for initial esr60 release.

Added
- Support of `firefox-esr-next-latest` and `firefox-esr-next-latest-ssl` aliases

Added
- bouncer aliases preflight checks - making sure the aliases match certain regexes

Changed
- `script.async_main()` relies on scriptworker (>= 10.2.0) to initialize context, config, and task
- `task.validate_task_schema()` now relies on scriptworker


Removed
- `script.usage()`, now handled by scriptworker
- `task.validate_task_schema()` now handled by scriptworker
- `load_json` now handled by scriptworker (moved it temporarily under tests until integration tests are added)

Added
- changelog
- 100% code-coverage
- production mode for bouncerscript