Added the ability to force completion through options & hid stdout reporting if a reporter was present

- Added the ability to force completion despite having errors through ``options: { force: true }``. This was a problem if attempting to run the task directly because --force is not possible and ``grunt.option('force', true)`` was not working 
- Significantly reduced noise by moving the ``grunt.log``s for warnings and errors into a conditional that only fires if another reporter is not present.