[Gruntfile template] - change all {,*/} to {,**/} so that they can go multiple levels deeper

The {,*/} wildcard only matches the current level and one level below. For example
```
"/styles/{,*/}*.css"
```
 will match "/styles/foo.css" and "/styles/foo/bar.css" but not "/styles/foo/bar/deep.css"

Changing the wildcard to {,**/} fixes this.