jQuery positional selectors () have been deprecated in
[jQuery 3.4.0](https://blog.jquery.com/2019/04/10/jquery-3-4-0-released/)
and they'll be removed in jQuery 4.0.0. This PR removes their usage.
Most of the changes were possible without changing public API. However,
dropping `:even` usage required a change to the
[`header` option](https://api.jqueryui.com/accordion/#option-header)
of the accordion widget. I made it an optional function; this will need
to be documented.
The polyfill for `.even()` & `.odd()` is added for jQuery <3.5.0. There was
no usage of the :odd selector in the code but the `.odd()` method is also
polyfilled for completeness.
Closes gh-1904
Adds a data-composite option and fixes paths for effects. Otherwise
just applies the same conversion as already applied to demos, sometimes
moving a <style> element to the right place.
1. Introduces a set of helper methods to easily create and define new effects.
2. Uses clip animations and placeholders instead of wrappers for clip effects.
3. Ensures all animations are detectable as animated
Fixes#10599Fixes#9477Fixes#9257Fixes#9066Fixes#8867Fixes#8671Fixes#8505Fixes#7885Fixes#7041
Closes gh-1017
