Hashing functions based upon openssl created

Hashing functions based upon openssl created

The following functions were implemented:
string hash_data(string data, algorithm algo=SHA1); // output: hex encoded hash
string hash_data_raw(string data, algorithm algo=SHA1); // output: raw binary hash
string hash_file(string filename, algorithm algo=SHA1); // hash data in 64kb blocks

Unit test also included.