Reworked linter and reporter so that there can be one per editor so that...

... in split view, things continue to work when switching between the views

https://github.com/MiguelCastillo/Brackets-InteractiveLinter/issues/55
There should be a `typeof` in front of `line` **or** remove the quotes around `undefined`.

Also, this is my fault, but `char: 0` should probably be `char: 1`. I remember seeing code somewhere that makes sure characters are at least 1.