Fixed bug in DropController.retrieve() where a special state led to a drop message be handled twice or more times. #200
Handle possible RuntimeExceptions that are likely to be caused by invalid Json syntax.
If this wasn't handled, consciously injected errornous JSON could crash the entire client.
Corrected DropController.decryptDrop() javadoc
Introduced deserialization tests for invalid/illegal JSON syntax in drop messages
Added rationale comment to DropController.retrieve() why InvalidKeyExceptions won't be handled
Pass DropController.sendAndForget() exception to logger for better stacktrace analysis
Pass exception in DropController.handleDrop() to logger
Merge pull request #213 from aBothe/pr3

Handle possible NullRef/JsonSyntaxException in Drop.deserialize()
Merge pull request #212 from aBothe/pr

Fixed DropController.retrieve()-Bug; Improved exception logging
added meanbean library to project for testing purposes
added test method for factory created instances
changed equals() method test for class Account:
* added EquivalentFactory for Account
* changed AccountEqualsTest to use MeanBean library
implemented equals() method test for class Identity:
* changed type of "drops" field to List as equals() method of Collection causes problems while testing
* added EquivalentFactory for instances of Identity
* added Factory for Collection<DropURL> for testing purposes
* added Factory for QblPrimaryKeyPair for testing purposes
added field primaryKeyPair to equals() method in class Identity
implemented equals() method test for class DropServer:
* added factory for URL instance creation for testing purposes
* added EquivalentFactory for equivalent instance creation of DropServer for testing purposes
* added test method for DropServer equals method test
Implemented equals() method test for class Contact:
* added EquivalentFactory for equivalent instance creation of contact for testing purposes
* added QblPrimaryPublicKeyFactory for testing purposes
* added IdentityFactory for testing purposes
* added equals() method test
added property primaryPublicKey to equals() method in class Contact
implemented equals() method test for class StorageServer:
* added EquivalenFactory of StorageServer for testing purposes
* added equals method test
implemented equals() method test for class StorageVolume:
* added EquivalentFactory for StorageVolume for testing purposes
* added test for equals() method
implemented equals() method test for class Accounts