Dynamic list of Tools

How can we provide a dynamic (not hard-coded) list of tools during Editor initialization?

The configuration object requires the Tool Class name be provided, with the Tool preloaded (so the class reference is valid):

```
tools: {
myOwnParagraph: MyParagraph
}
```

The `MyParagraph` tool needs to be preloaded before this object is constructed. There's no way to pass in a configuration, say from a decoded JSON string passed to the page, since `MyParagraph` would be a string, not a plain class name.

It would be _fantastic_ if the `tools` object could be in a JSON-friendly format so that we can pass a list of tools from the backend, unique to each editor instance.

Suggestions?