Fix kredits balance handling

Kredits are stored on the Token contract as uint256 / bignumbers with 18
decimal points. Just like Ether and required by the ERC20 standard.
So we need to work with bignumbers and format a bignumber value here.

app/utils/cps/kredits.js

@@ -0,0 +1,25 @@
+import { computed } from '@ember/object';
+import ethers from 'npm:ethers';
+//import formatKredits from 'kredits-web/utils/format-kredits.js';
+
+function formatKredits(value, options) {
+  let etherValue = ethers.utils.formatEther(value);
+  if (!options.decimals) {
+    etherValue = parseInt(etherValue).toString();
+  }
+  return etherValue;
+}
+
+export default function(dependentKey, options = {}) {
+  return computed(dependentKey, {
+    get () {
+      const value = this.get(dependentKey);
+      return formatKredits(value, options);
+    },
+    set (key, value) {
+      const bnValue = ethers.utils.bigNumberify(value);
+      this.set(dependentKey, bnValue);
+      return formatKredits(bnValue, options);
+    }
+  });
+}