A render optimization algorithm for refreshing the UI via props tunnelling (setting new props on a component's
state in a pre-agreed location). This algorithm analyzes database changes and on-screen components to update
components (by ident) whose props have changed.

Prop change detection is done by scanning the database in *only* the locations that on-screen components are querying
(derived by the mounted component idents, and any ident-joins in the queries).

The keyframe optimized render.

Just like keyframe render, but supports `:only-refresh` option.

(defonce app (app/fulcro-app {:optimized-render! mroot/render!}))

(defsc AltRoot [this {:keys [alt-child]}]
  ;; query is from ROOT of the db, just like normal root.
  {:query                 [{:alt-child (comp/get-query OtherChild)}]
   :componentDidMount     (fn [this] (mroot/register-root! this {:app app}))
   :componentWillUnmount  (fn [this] (mroot/deregister-root! this {:app app}))
   :shouldComponentUpdate (fn [] true)
   :initial-state         {:alt-child [{:id 1 :n 22}
                                       {:id 2 :n 44}]}}
  (dom/div
    (mapv ui-other-child alt-child)))

;; For use in the body of normal defsc components.
(def ui-alt-root (mroot/floating-root-factory AltRoot))

;; For use as plain React class
(def PlainAltRoot (mroot/floating-root-react-class AltRoot app))

...

(some-js-library #js {:thing PlainAltRoot})

(defsc NormalFulcroClass [this props]
  {:query [:stuff]
   :ident (fn [] [:x 1])
   ...}
  (dom/div
    ;; ok to use within defsc components:
    (ui-alt-root)
    ;; how to use the plain react class, which is how js libs would use it:
    (dom/create-element PlainAltRoot)))

Like keyframe-render2, but also supports free-floating roots.

WARNING: THIS RENDERER IS ALPHA. Lightly tested, but not heavily used yet.

General usage:

1. Set this nses `render!` as your application's optimized render function.
2. Create a class that follows all of the normal rules for a Fulcro root (no ident, has initial state,
composes children queries/initial-state, etc.
   a. Add mount/unmount register/deregister calls
2. Use floating-root-factory to generate a Fulcro factory, or floating-root-react-class to generate
a vanilla React wrapper class that renders the new root.
   a. Use the factory in normal Fuclro rendering, but don't pass it props, or
   b. Use `(dom/create-element ReactClass)` to render the vanilla wrapper, or
   c. Use the vanilla wrapper class when a js library controls rendering (like routing).

Example:

```
(defonce app (app/fulcro-app {:optimized-render! mroot/render!}))

(defsc AltRoot [this {:keys [alt-child]}]
  ;; query is from ROOT of the db, just like normal root.
  {:query                 [{:alt-child (comp/get-query OtherChild)}]
   :componentDidMount     (fn [this] (mroot/register-root! this {:app app}))
   :componentWillUnmount  (fn [this] (mroot/deregister-root! this {:app app}))
   :shouldComponentUpdate (fn [] true)
   :initial-state         {:alt-child [{:id 1 :n 22}
                                       {:id 2 :n 44}]}}
  (dom/div
    (mapv ui-other-child alt-child)))

;; For use in the body of normal defsc components.
(def ui-alt-root (mroot/floating-root-factory AltRoot))

;; For use as plain React class
(def PlainAltRoot (mroot/floating-root-react-class AltRoot app))

...

(some-js-library #js {:thing PlainAltRoot})

(defsc NormalFulcroClass [this props]
  {:query [:stuff]
   :ident (fn [] [:x 1])
   ...}
  (dom/div
    ;; ok to use within defsc components:
    (ui-alt-root)
    ;; how to use the plain react class, which is how js libs would use it:
    (dom/create-element PlainAltRoot)))

```