Fix #39, #61, #62 (and may be other bugs) issues with merging options on initial/update fromJS and toJS functional.
Fix #39, #61, #62 (and may be other bugs) issues with merging options on initial/update fromJS and toJS functional.

1) Options for root mapping are merged in priority: current (higher), previous, default (never overwritten) options.
2) Options for nested mapping are not mergeable (cannot merge current options for root with nested) that why we use always previous.

gregoriusxu/knockout.mapping,lucaslago/knockout.mapping,gregoriusxu/knockout.mapping,tilhom/knockout.mapping,lucaslago/knockout.mapping,tilhom/knockout.mapping,mespaceintime/knockout.mapping,humbleBeginner/knockout.mapping,SteveSanderson/knockout.mapping,amilachamikara/knockout.mapping,wikieswan/knockout.mapping,gregoriusxu/knockout.mapping,humbleBeginner/knockout.mapping,drewwestphal/knockout.mapping,mespaceintime/knockout.mapping,LittleHelicase/knockout.mapping,jesulink2514/knockout.mapping,tilhom/knockout.mapping,drewwestphal/knockout.mapping,humbleBeginner/knockout.mapping,jesulink2514/knockout.mapping,LittleHelicase/knockout.mapping,lucaslago/knockout.mapping,drewwestphal/knockout.mapping,wikieswan/knockout.mapping,wikieswan/knockout.mapping,mespaceintime/knockout.mapping,amilachamikara/knockout.mapping,amilachamikara/knockout.mapping,jesulink2514/knockout.mapping