CRM-20600 - Move Angular metadata to civix-style files

CRM-20600 - Move Angular metadata to civix-style files

This PR moves the metadata about Angular modules out of Civi\Angular\Manager
and into standalone files (`ang/*.ang.php`).  This uses the same structure
as `civix`.  Also, this makes it easier to navigate between the
JS/HTML/CSS/PHP content.

To test that these changes were safe, I ran the following command before and
after this commit:

$ cv ev 'var_dump(Civi::service("angular")->getModules());'

The results were substantively identical.