added calc hmac function
Added HMAC and GCM en- and decryption
Added HMAC test
changed the hmac test (works with test cases)
edited symmetric decrypt test
rearranged symmetric crypto tests
rearranged symmetric crypto tests again
added hmca validation test
added logging of invalid hmac and auth tag
devided hmac validation test into two
Merge pull request #96 from roeslpa/HMAC
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>