Adding force to update routine

- Introduced Cache::NEVER Lock (never expiring lock)
- Force flag for dbstructure update
- Moving the business logic to central place in Update class

src/Core/Cache.php

@@ -19,6 +19,7 @@ class Cache extends \Friendica\BaseObject
 	const QUARTER_HOUR = 900;
 	const FIVE_MINUTES = 300;
 	const MINUTE       = 60;
+	const NEVER        = 0;
 
 	/**
 	 * @var Cache\ICacheDriver