Extract scene functions to their respective modules (#208)

- Also, extract utilities into utils module -- capitalizeString, getDateTime, isInputLike

src/scene/index.ts

@@ -0,0 +1,19 @@
+export { isOverScrollBars } from "./scrollbars";
+export { renderScene } from "./render";
+export {
+  clearSelection,
+  getSelectedIndices,
+  deleteSelectedElements,
+  someElementIsSelected,
+  setSelection,
+  getSelectedAttribute
+} from "./selection";
+export {
+  exportAsPNG,
+  loadFromJSON,
+  saveAsJSON,
+  restoreFromLocalStorage,
+  saveToLocalStorage
+} from "./data";
+export { hasBackground, hasStroke, getElementAtPosition } from "./comparisons";
+export { createScene } from "./createScene";