Unit test Entity deletion and research

Added tests, documentation, pragma for Entity deletion and search.

I have also added the following method

```swift
class func deleteAll(predicate: NSPredicate!, context: NSManagedObjectContext =
SuperCoreDataStack.defaultStack.managedObjectContext!) -> Void
```
cool, one tiny thing, they are under the Entity Search Pragma Mark rather than Object Lifecycle / Deletions or similar.