Unit tests: Use new names of module hooks

Refs http://qunitjs.com/upgrade-guide-2.x/#replace-qunit-jsdump-with-qunit-dump

Refs http://qunitjs.com/upgrade-guide-2.x/#replace-qunit-log-callback-with-qunit-log-callback-for-all-reporting-callbacks

Refs #15893

Modal: Apply any preexisting body padding again after closing

Closes #15291 by merging it.

Fixed performance bug where a tooltip element is created and then immediately destroyed when tooltip.hide() is called and there is no existing tooltip element

Resolves #15557 by merging it.

Fixes #15147.
Closes #15520 by merging it.

[Ref #15881] Use Explicit JS Variable Declarations rather than Chained

tip method in popover.js can be removed

[Ref #15881] Use Explicit Values for javascript variables rather than chained ones.

From https://github.com/twbs/bootstrap/pull/15881#discussion_r25330647

Add source code documentation of justified navbar for #15906

docs > js > headings

Document in the source code that the justified nav is meant for single line list items only. This should help prevent Issues like #15906 in the future.

Fixes #15106.
Closes #15910.

ScrollSpy: Small style consistency adjustments

[Docs—Fixes #15882]Use an ID as the example for Scrollspy

Updated license links

docs>components>labels headings

docs>components>progress bars headings

Add plugin package keyword recommendation

docs>components>(remaining components) headings

docs>components>media object headings

docs>components>thumbnails headings