Added support for decrypting PDF 1.7/2.0 Algorithm 5 revision 5 and 6.

*Added AES128 Encryption
*Added AES258 Encryption/Decryption
*Added SHA256
*Added SHA512
*Added class to handle 8 byte integers and associated bit operations
*Added SHA384
*Added routines to handle new algorithm and perform PDF2.0 hashing.

This resolves #2647
Also resolves #1828