Update Change number of drops in Identity class
Fixed  Identity constructor should set QblPrimaryKeyPair #128
added registration of QblPrimaryKeyPairTypeAdapter in IdentitiesTypeAdapter
Update List to Collection.
add addDrops()
getDrops() returns a immutable collection
Don't return null when being unable to deserialize a DropMessage's data entry.
DropMessage ctor bug
Init DropMessage's acknowledgeID with "0" instead of an empty string, as this is stated in the docs #156
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
Naming in drop message was wrong