Added regression test

For sending and receiving encryptped / decrypt (non) multi part drop messages.
Merge pull request #119 from L-Henke/negativeArrayBug

Fixed array initialization with negative size in CrypoUtils
Merge pull request #121 from thechauffeur/debug_multipart

Added regression test
equalized dropserver ports
Merge pull request #124 from jan-schreib/equalize-ports

equalized dropserver ports
Fixed constructor of Identity

The constructor of Identity was always setting the primaryKeyPair to an
uninitialized value
Removed unneeded QblEncPublicKey and QblSignPublicKey from Contact

These two are part of the primary public key
Added additional log messages to CryptoUtils decryptHybrid...
Changed the return type of DropHTTP receiveMessages to Collection<byte[]>

DropHTTP was sending out byte arrays but parsed received messages as
strings. This was modifiying the messages which results in the invalid
signature.

The DropTest is also modified. Class variables has been replaced with
methods variable, to avoid unintended behaviour when different tests are
using the same variables.

Also retrieveTest() is not an own JUnit test anymore, because these are
called in undefined order. Instead, this function is now called from the
send tests.

Since the keys are generated random for each run, we only expect one
drop message do be decryptable. Older messages were created with
different keys.
Changed attachXPublicKey to public

Added log messages for attaching invalid sub public keys
Adapted MultiPartCryptoTest to new Identity constrctor