feat(command): add output option to ng lint command

[moritz-h]

Add output option to ng lint command to redirect lint result to file.

Fix #4791

[filipesilva]

Heya, we try to avoid these output commands in general since you can just use console pipes to redirect output (e.g. ng lint > log.txt).

If that's not working it would be better to fix the broken code instead of providing an output option. In the case of #4791 it seems like the checkstyle format should have a special output format, with only xml.

[moritz-h]

@filipesilva
To fix the code would it be ok to just remove this 2 lines:
ui.writeLine(chalk.red('Lint errors found in the listed files.'));
ui.writeLine(chalk.green('All files pass linting.'));
from here: https://github.com/angular/angular-cli/blob/master/packages/%40angular/cli/tasks/lint.ts#L64-L71
Then using piping is fine no matter what format. Or do you want this lines for default output?

Or is it somehow possible to print these lines to stderr so you can pipe ng lint 1> log.txt?

[filipesilva]

Those lines should stay overall, but you can specialcase the xml format to not output them. You should also fix the success xml output for that one.

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