Common reorg (#8025)

* Re-organize common folder

* fix: Correct paths in tests

* fix: move new content to proper folder

* chore: Move audio folder to assets

* Move sprites to sprites assets directory

* Move css sprites to assets directory

* Split out readmes for common code and sprites

* Move images to assets directory

* Move destinatin of shared browserified file

* remove unused file

* move compiled js to client-old

* Fix karma tests

* fix: Correct paths for sprites

website/common/script/statHelpers.js

@@ -0,0 +1,38 @@
+import {
+  MAX_LEVEL,
+} from './constants';
+
+/*
+  ------------------------------------------------------
+  Level cap
+  ------------------------------------------------------
+ */
+
+export function capByLevel (lvl) {
+  if (lvl > MAX_LEVEL) {
+    return MAX_LEVEL;
+  } else {
+    return lvl;
+  }
+}
+
+/*
+  ------------------------------------------------------
+  Scoring
+  ------------------------------------------------------
+ */
+
+export function toNextLevel (lvl) {
+  return Math.round((Math.pow(lvl, 2) * 0.25 + 10 * lvl + 139.75) / 10) * 10;
+}
+
+/*
+  A hyperbola function that creates diminishing returns, so you can't go to infinite (eg, with Exp gain).
+  {max} The asymptote
+  {bonus} All the numbers combined for your point bonus (eg, task.value * user.stats.int * critChance, etc)
+  {halfway} (optional) the point at which the graph starts bending
+ */
+
+export function diminishingReturns (bonus, max, halfway = max / 2) {
+  return max * (bonus / (bonus + halfway));
+}