Update Change number of drops in Identity class
Fixed  Identity constructor should set QblPrimaryKeyPair #128
Commented CryptoUtils
Prop init cosmetics
Merge pull request #152 from aBothe/master

Small code cosmetics.
Don't return null when being unable to deserialize a DropMessage's data entry.
added registration of QblPrimaryKeyPairTypeAdapter in IdentitiesTypeAdapter
DropMessage ctor bug
Init DropMessage's acknowledgeID with "0" instead of an empty string, as this is stated in the docs #156
Update List to Collection.
add addDrops()
getDrops() returns a immutable collection
Merge pull request #148 from k-c13/identity-drop-key

Fixed  #109 (Update Change number of drops in Identity class) and #128 (Fixed Identity constructor should set QblPrimaryKeyPair)
Merge pull request #153 from aBothe/pr

Don't return null when being unable to deserialize a DropMessage's data field
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