Settings: Admin User Tab

closes #2422

- updated to use new change password method
- have all save settings use notifications
- create assetSrc helper for creating asset paths with subdir's properly
 prefixed
hehe.

Thought was b/c in an image tag you assign its src attribute.

However when coding having this be an exception to the rule would violate intuition.

I'll change it to `assetUrl`.

To take it further, what do you say I change all the `<pre>Url` things to:

```
url: {
  admin: fn
  api: fn
  asset: fn
}
```
And now we're as dry as a bone.