Added `transform` to the SA options - Not tested yet

* Added `FS.Transform` *remove from base package..*
* Added `transform`/`transformTo`
* Added `transformFrom`
* Added `FS.Transform.scope` here packages can add helpers to the
transform scope

It should be possible to:
```js
  var images = new FS.Collection(‘images’, {store: [
    new FS.Store.FileSystem(‘local’, {
      path: ‘/foo/bar’,
      transform: function(fileObj, readStream, writeStream) {
        this.gm(readStream).resize(10).stream().pipe(writeStream);
      }
    })
  ]});
```
> transform and transformTo are same thing - transformFrom is getting
the data back, eg. if crypt/decrypting data from to storage…

cc @aldeed