Add possibility to log all lint erros if the user use the shortcut

I find it useful to have the possibility to display all errors and click on the error to go to the correct line/col.

I implement this feature and it works only when you are using the linter shortcut (because I also want to keep the old behavior).

![atomlinter](https://cloud.githubusercontent.com/assets/1850538/3978589/c5444108-2849-11e4-8b64-5508f24c61a6.gif)

I would like to know if you find this feature useful.

If so, I still have some works to do on this PR:
  - Adding specs
  - I don't like the way how I get the line number/col of the error. Need to think about a better solution.

Good point. Atom's settings stuff definitely needs a radio button widget. How about we agree it's ok to make things a bit worse for now and separate confusing options out into a separate issue that can be fixed at a later time.

How about renaming your new option to `showAllErrorsInStatusBar` though? Then the meaning is clearer.