Remove outcommented code from Subscription.php
Move functionality from hasModelFeedUpdates to a new function getFilesForFeedUpdates

- getFilesForFeedUpdates returns a list of files with feed updates
related to the selected model
Refactor code and add some comments
Reorder functions and add comments
Simplify if clause
Remove hasModelFeedUpdates and move its code to shouldShow function
Move feed update handling to own class PubSubHubbub/FeedUpdate.php
Make it possible to import feed updates for all resources of the selected model

- there is a new button in modelinfo view
Add script to reinstall hub server (removes folder first, after install it again)