Support in os-brick for "Image Encryption and Decryption"

The methods for encryption and decryption of files - in this case images - will be written in a driver like manner in os-brick so the image encryption can be extended with another encryption format easily. The encryption driver should focus a specific encryption format and implement exactly one encrypt and one decrypt method, both based on a cipher implementation of GPG aes. This driver may be simple wrappers around an existing implementation. An abstract base class should be defined and be used for the implementation of GPG encryption (and might be used for other implementations in the future).