Allow string values in JSHint's "unused" and "latedef" options

Hi,

JSHint now allows both boolean and string values for options ["unused"](http://jshint.com/docs/options/#unused) and ["latedef"](http://jshint.com/docs/options/#latedef), but SharpLinter was only allowing boolean values.
Here's a patch that allows settings both bool/string values for these two options. It declares the options as being of type object, and JsLintConfiguration.SetOption() takes care of putting a real bool or string value depending of what's being read.
The tests are still passing, and my own eyeball testing found no problems :)

Feel free to yell at me if I did anything the wrong way, this is my first pull request ^_^