* When --noUnusedLocals/--noUnusedParameters is disabled, add suggestions instead of errors
* Improve performance: do not add unused suggestion diagnostics unless asking for a suggestion
* Add "unused" flag to diagnostics
* Code review
* reportsUnused -> reportsUnnecessary
* Fix test
1. Object literals are single-line now.
2. Index signatures transform to TS index signatures.
3. The refactoring is only available when it could add types.