Finished user registration functionality

1. Corrected issues with UserResource calling non-existant exception
classes.
2. Added $guarded property to User model, and corrected validation
observer call.
3. Corrected issues with PostSqlMapper, changed generateSqlArray() to
postToSql(), and added sqlToPost().
4. Corrected issue with BaseLaravelValidator usingInput() not returning
$this (thus preventing method chaining).
5. Corrected issue with BaseLaravelValidator getErrors() where it was
only returning messages, not the input ID associated with the messages.
6. Corrected exception class calls in UserObserver.
7. Added call to PostSqlMapper::sqlToPost() in UserObserver validation
exceptions to convert SQL inputs back to the POST inputs.
8. Fixed issue with UserValidator->usingRule() not returning $this.
9. Added missing "use" line to ValidatorFactory.
10. Moved UserResource route out of the password-protected group.
11. Added OnLibrary JS file and User Registration Page JS file.
12. Updated base.blade.php to include onlibrary.js and a siteUrl
variable.
13. Updated register.blade.php to allow form to be submitted via AJAX.