Fix https://github.com/angular/angular-cli/issues/4138
BREAKING CHANGE:
- `--extractCss` defaults to `false` on all `--dev` (`ng build` with no flags uses `--dev`)
- `--aot` defaults to true in `--prod`
- the alias for `--output-path` is now `-op` instead of `-o`
Having css extraction on all the time makes dev rebuild times very slow for global styles.
This flag defaults to false on dev targets and true on prod targets.