Update Change number of drops in Identity class
Fixed  Identity constructor should set QblPrimaryKeyPair #128
Update class diagram
Merge pull request #149 from k-c13/update-model

Update class diagram
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