added javadoc to class Account
added javadoc in class Accounts
added javadoc in class Contact
added javadoc in class Contacts
added javadoc in class DropServer
added javadoc in class DropServers
added javadoc in class Identity
added javadoc in class LocalSettings
added javadoc in class Settings
added javadoc in class StorageServer
added javadoc in class StorageServers
added javadoc in class StorageVolume
added javadoc in class StorageVolumes
added javadoc in class SyncedSettings
Update class diagram
Merged class Drop into DropController

closes #112.

* Moved functions from Drop.java into DropController.java
* Deleted Drop.java
* Renamed DropTest.java to DropControllerTest.java