rewrite OTData, new ot_data_t typedef
update OTCrypto to make use of new OTData
update OTASCIIArmor to make use of new OTData
update OTEnvelope to make use of new OTData
update OTSymmetricKey to make use of new OTData
headers updated to make use of new OTData
updated OTAsymmetricKey to make use of new OTData
updated ot core to make use of new OTData
udpated remaining ot to make use of new OTData