added gson to dependecies in build.gradle
changed gson version to 2.+
Added CryptoUtils singleton class
Merge pull request #15 from f-porter/Issue-14-AddGson

added gson to dependecies in build.gradle
Added getSHA512sum(byte[]) method to cryptoutils
Changed names of constants
CryptoUtils singleton is now thread safe
Merge pull request #19 from L-Henke/cryptoutils

Added CryptoUtils singleton class
Added QblKeyPair and QblPublicKey classes
Changed creation of public key fingerprint method. The hash is now created over a byte array with the modulus and the exponent.
Moved key pair test from ConfigTest to CryptoTest
Merge pull request #20 from L-Henke/keyPairs

Added QblKeyPair and QblPublicKey classes
Changed comments to valid Javadoc
Merge pull request #23 from L-Henke/cryptoutils

Changed comments to valid Javadoc
setURL(URL value) is checking the drop-ID now

* drop-ID needs a size of 43 chars.
* drop-ID needs to be base64 encoded.

implemented length checking
implemented 3 tests for the setURL() logic.

* valid url test
* too short url test
* too long url test
removed unneeded toString() functions.

the test urls are valid.
added missing exception; renamed dropUrl to dropID
added base64 check for setUrl()
added test for base64 check and for null