Introduce exception mapper - remove exception mapping code redundancy

[mlotysz]

You map exceptions in all your resource methods:

        try {
            actor = dao.findById(id);
        } catch (DataAccessException e) {
            throw new NotFoundException(e.getMessage());
        }

Remove exception mapping code redundancy by creating exception mapper. Start here: http://www.dropwizard.io/0.9.2/docs/manual/core.html#error-handling