Refactor empty and loading views in a custom view

Empty view / loading view refactor. All is now managed in a single custom view.

This is WIP, waiting for !264 (merged) to be merged to handle the complex rebasing.

changed milestone to %3.3

changed the description

added 19 commits

• c8a958d7...bacbd238 - 18 commits from branch videolan:master
• e68de31d - Refactor empty and loading views in a custom view

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unmarked as a Work In Progress

added 8 commits

• e68de31d...312932f0 - 7 commits from branch videolan:master
• 0b10fb3f - Refactor empty and loading views in a custom view

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added 22 commits

• 0b10fb3f...ab7e9a4d - 21 commits from branch videolan:master
• 243013f4 - Refactor empty and loading views in a custom view

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We still see the empty view during loading.

Also, the "Add media to medialibrary' button is briefly visible on browser.

added 1 commit

• 464cf549 - Refactor empty and loading views in a custom view

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Fixed

added 10 commits

• 464cf549...858fad50 - 9 commits from branch videolan:master
• 2e8d7aae - Refactor empty and loading views in a custom view

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merged

mentioned in issue #1050 (closed)