Include Ownership in the Ship of Theseus

When we determine whether a React component should be updated (as opposed to destroyed or replaced), we currently only look at whether they share the same constructor. This adds a check for whether they share the same owner component.

I've also consolidated this logic (I cannot believe this was not already done).
Move merge utility functions from utils to vendor/core
add docs lowercase mention for data- and aria-
Merge pull request #482 from chenglou/data-lowercase

add docs lowercase mention for data- and aria-