Implement 'Resolve to this Sibling' button in Object view

[dmitrizagidulin]

When an object has siblings, allow the user to select a sibling and resolve the conflict to the one selected. (Currently, we just list the siblings, and objects with siblings are un-editable through the GUI).

See:

• http://docs.basho.com/riak/latest/dev/using/conflict-resolution/#Siblings
• http://docs.basho.com/riak/latest/dev/references/http/fetch-object/#Siblings-examples