Fixed  #109 (Update Change number of drops in Identity class) and #128 (Fixed Identity constructor should set QblPrimaryKeyPair)

Update Change number of drops in Identity class #109 
Fixed  Identity constructor should set QblPrimaryKeyPair #128

Please also check the issue #147 because a test crashed
Well, read-only is debatable. I'd indeed prefer returning immutable collection and providing a "addDrop" method in the Identity class.
But, as you well spotted, Collection are generally mutable and I think there is no need to expose the List-character of this datastructure.