Changed all Cipher and Signature method variables to object variables
Fixed Javadoc
Changed all non-private CryptoUtils methods to synchronized
CryptoUtils now throws RuntimeExceptions for fatal initialization errors
Refactored exception handling in CryptoUtils.
Exceptions which are the result of invalid input values are now thrown
Changed Mac method variable to object variable
Merge pull request #161 from L-Henke/cryptoUtilsRefactor

CryptoUtils refactorization
Fix #111 Drop::sendAndForget can return a false value
Move DropResult and DropResultPair to a new class
Update DropMessage<T> to DropMessage<? extends ModelObject>
Fix #111 Drop::sendAndForget can return a false value
Move DropResult and DropResultPair to a new class
Fixed #165 Wrong (or naive) documentation of Drop.send()
Update DropMessage<T> to DropMessage<? extends ModelObject>