Automatically detect requirements in *.aff.html

Automatically detect requirements in *.aff.html

PART A: EXPORT LIST

Suppose you create a form `downstreamForm.aff.html`.

The metadata for `downstreamForm` will indicate that it exports an element `<downstream-form/>`:

```php
$angularModules['downstreamForm']['exports']['el'] = ['downstream-form'];
```

PART B: AUTO-REQUIRES

Suppose that:

1. he form `downstreamForm.aff.html` uses element `<upstream-el/>`.
2. The `$angularModules['upsteamMod']['exports']['el']` defines an exported element `upstream-el`.

Then the `downstreamForm` module will automatically requires the `upstreamMod`, as in

```php
$angularModules['downstreamForm']['requires'][] = 'upstreamMod';
```