Explicit render parameters when making components from spec

Render is require for all React components so we make it a parameter for
mkUIFromSpec and mkStatefulUIFromSpec. Now their types correspond to mkUI and
mkStatefulUI but with an additional spec parameter:

    mkUIFromSpec ::
      forall props.
      Render props
      -> UISpec props
      -> (props -> UI)

    mkStatefulUIFromSpec ::
      forall props state.
      state
      -> StatefulRender props state
      -> StatefulUISpec props state
      -> (props -> UI)