fix($core): register async page/layout components and pascalize their names (close: #1173, #1321, #1391) [WIP]

[shigma]

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[shigma]

cc @meteorlxy

[ulivz]

The components of a page should be registered ONLY when they are used, otherwise and you’ll be switched to a new page even if your content of asynchronous page has not been loaded, - this experience is too strange, besides, the current state of nprogress is wrong.

[ulivz]

Closing it in favor of 9d01514, 0306574 and 3e91eba