Improve sync file structure

[RyanBayne]

Currently we have class.twitchpress-sync.php and the class includes admin and public UI output for edit user views.

• We need to create a class that focuses on modifying the edit user view and move the HTML from the sync class to the new class.
• We need to create a "sync" folder for placing multiple classes in (one for each sync task).
• Then create a "twitch" folder within "sync" for Twitch data tasks
• Now create a file in the twitch folder for subscription syncing
• Finally move subscription syncing from class.twitchpress-sync.php to the new file

The current sink class will be extended and the class will slowly focus on controlling the sync queue and executing task in a suitable way.

[RyanBayne]

The applicable class has been worked on and renamed since this issue was created.