Add all of the Mobile meta tags to 8.x-1.x

I'm going to work today on this issue during the Drupal Developers Days at Milan

Here is a first patch with wich includes a first approach for migrating the metatag_mobile submodule to D8.

After some hours migrating by hand the old metatags types to the new metatag plugin system, I hacked locally the generate:tag command for generate automatically the plugins based on the implementation of D7. Because of this some classnames are not so accurate, but at least most of the work is automated and we'll only have to edit some stuffs.

During the migration process I had some doubts:

1. Secure parameter: How can I identify this parameter in the old implementation of a metatag?
2. Some of the metatags at the D7 version have something like: '#theme' => 'a custom theme here',, for example:
   

   $info['tags']['x-ua-compatible'] = array(
       'label' => t('X-UA-Compatible'),
       'description' => t('Indicates to IE which rendering engine should be used for the current page.'),
       'weight' => ++$weight,
       'element' => array(
         '#theme' => 'metatag_http_equiv',
       ),
     ) + $tag_info_defaults;
   

   How should be this implemented at the new plugin system?

3. Some of the metatags at the D7 version have something like: 'header' => FALSE, How should be this implemented in the new plugin type?

NOTE: Big thanks to @penyaskito for giving me the idea of trying to automate the migration of the plugin implementations. Much funnier than doing it by hand.

Thanks @DamienMckenna for your awesome work one more time!