created new security library

Ignore-this: 2b1fe47c27f655ed701732a1b8aa6ce6

moved util/security to this new library. It will contain all the code dealing
with encryption/decryption and keep the communication secret.

darcs-hash:20130725040009-c21fe-24a29b7bd517b89493e160f3b50b2ed9a62fdd58