Changed the version from an int to a String to be more flexible.
added this enum to describe the inchat format keys (as in json, there are key/value pairs).
needed for CryptoPacker.
changed the id to a byte array since this is simpler and more intuitive. in the end, the id is just a large random number. also added the asymmetric key pair to the participant. i think it belongs there...
added a method to calculate a digest of a given message. this is necessary to verify the integrity of a message.
added a participant id  generator to easily generate ids for new participants. this just takes some entropy and calculates the sha-256 digest of that.
improved an exception test.
a first version of the crypto packer, that allows to encrypt-and-pack and unpack-and-decrypt messages. there are still a few problems which will be fixed in the next days (hopefully).
an unfinished outine of the transfer graph parts. this need a lot of work. this commit is just to share it with others (and to my notebook...).
moved