Rename `domUtils` to `dom`

src/dom/CSSProperty.js renamed

src/dom/CSSPropertyOperations.js renamed

src/dom/DOMChildrenOperations.js renamed

src/dom/DOMProperty.js renamed

src/dom/DOMPropertyOperations.js renamed

src/dom/Danger.js renamed

src/dom/__tests__/CSSPropertyOperations-test.js renamed

src/dom/__tests__/DOMPropertyOperations-test.js renamed

src/dom/dangerousStyleValue.js renamed

src/dom/getDOMNodeID.js renamed

src/dom/getTextContentAccessor.js renamed

src/dom/insertNodeAt.js renamed

src/dom/isEventSupported.js renamed