BREAKING(Ref): add support for forwardRef API

[layershifter]

Fixes #3255.

---

This PR implements support of forwardRef API. This allows to implement more correct behavior and provides ability to careful control of refs.

Affects Modal, Popup and Sidebar components. If you're using components without forwardRef() nothing will change for you. Can be breaking in some cases, see details below.

const ExampleButton = React.forwardRef((props, ref) => (
  <div>
    <button {...props} ref={ref} />
  </div>
))
const buttonRef = React.createRef()

render(
  <Ref innerRef={buttonRef}>
    <ExampleButton>Example</ExampleButton>
  </Ref>
)

Before

buttonRef.current // will point to `div`

After

buttonRef.current // will point to `button`

[codecov-io]

Codecov Report

Merging #3405 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3405      +/-   ##
==========================================
+ Coverage   99.89%   99.89%   +<.01%     
==========================================
  Files         170      172       +2     
  Lines        2818     2830      +12     
==========================================
+ Hits         2815     2827      +12     
  Misses          3        3

Impacted Files	Coverage Δ
src/addons/Ref/RefFindNode.js	100% <100%> (ø)
src/addons/Ref/RefForward.js	100% <100%> (ø)
src/addons/Ref/Ref.js	100% <100%> (ø)	⬆️

---

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[levithomason]

Released in semantic-ui-react@0.85.0.