Using Bundles makes passing data easier and does not need to redefine
the interface if the internel functions change.
The helper class has been updated accordingly. In addition, it wrappes
completely around all input and output (if wanted).
Provides an AIDL-API for other apps to encrypt and decrypt a string
symmetrically with a passphrase. Function names and API is by no way
finalized and will change!
Support for asymetric encription will follow.
For reference and discussion see issue #71,
https://code.google.com/p/android-privacy-guard/issues/detail?id=71