Database migrations + activerecord

Pakket will throw an error if you haven't configured a database. How do we deal with this, should there be an option to use a database or something?

**Sample migration usage**

`php vendor/bin/phinx init`
`php vendor/bin/phinx create AddUserTable`
`php vendor/bin/phinx migrate -e development`

**Sample activerecord model**

`app/models/User.php`

**Known code violations**
  * `app/models/User.php` needs class refactoring to use proper psr-4. I'm not too familiar with this yet.

**Known limitations**
  * The adapter between Phinx and ActiveRecord supports MySQL only at the moment. (config/database.php)
  * The adapter only supports the default Phinx environments at the moment: production/testing/development, custom environments will not work
Sidenote: we should do something about relative paths. There are currently some directory constants defined in `index.php` but maybe we should look into adding those to config.