Add 'appendMessageToParent' configuration option.

Hi,

Thank you very much for the development of Knockout-Validation, it's really great!
I am submitting this pull request because in our project the inputs that we want to validate may have a small icon by their side, and we want the validation messages to be displayed after those icons.
Thinking about that, I added a configuration that allows developers to configure Knockout-Validation so that validation messages can be appended to the parent node of the input element, instead of having them inserted after the input.

Please let me know if you have any questions, comments or concerns with this approach.
I think this can be really useful, and I will be more than happy to make adjustments as you deem necessary.

Thank a bunch!

Luiz