make pages public so they can be re-used

@prettyboymp 

If we keep this public I can add additional groups and settings in other files

example:

first-file.php
```
Voce_Settings_API::GetInstance()
  ->add_page('Global Site Settings', 'Global Site Settings', 'global-site-settings', '', '')
  ->add_group('Connect Services', 'connect-services')
  ->add_setting('Facebook Account Link', 'facebook_link')
```

another_module_file.php

````
Voce_Settings_API::GetInstance()
  ->settings_pages['global-site-settings']
  ->add_group( 'Twitter Authentication', 'twitter-auth' )
  ->add_setting( 'Consumer Key', 'twitter_consumer_key' )

```

You could also write a getter method for the setting page if you didn't want to make this public