base: jquery-form loaded via require.js

**Problem**

Occuring in production mode (`ASSETS_DEBUG=False`) on the homepage.

```
jquery.js: TypeError: require(...)(...) is not a function
almond.js: Error: undefined missing jquery-form
```

**Solution**
* uses the `requirejs` filters on `jquery` bundle.
* renames `legacy.js -> init.js` to match the naming used for search and deposit modules.