Improve configuration and initialization

[crissdev]

Currently the library initializes itself - without the need to call ko.validation.init. Also, binding handles like value, textInput etc. are automatically wrapped to become validatable. This adds difficulties in working with libraries like knockout-es5 or to prevent the registration. Furthermore, some may already define extenders which this library registers. Ideally, changes to this feature should not cause any breaking changes.

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Related issues:
#477 Opt-out option for makeBindingHandlerValidatable
#478 Calling ko.validation.group on object makes all observables validatable
#404 RegisterExtenders invoked before Init, cannot avoid adding rules to ko.extends
#150 Exposing default options
#192 Add option asyncOnModified (Related issue #180)

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More investigation is needed for the following issues:
#540 Support live option for observable objects
#49 Changing validation rules on the fly