Add a lint indicator for Interactive Linter linting

Removes default Brackets lint status indicator.
Replaces the `errorIndicator` with this `lintIndicator`.

See #61 for more detail on the reasons for this. 
By spreading I mean that if `messages = [ {test: "test1" }, {test: "test2" }, {test: "test3" } ]`, then this will be the call of the handler: `handler(evt, {test: "test1" }, {test: "test2" }, {test: "test3" })`