one package for all the hashes

[piyush-kurur]

Currently we have a package for all sha family hashes. The idea was to keep a minimal
core i.e. hashes that are more or less standard. Therefore hashes that are not in the SHA family will have to be implemented in a separate package.

While justified in a way, I think it might be better to have all hash related stuff in one package called raaz-hash. It could mean the following rearrangement of modules.

Apart from the raaz-hash-sha package being renamed to raaz-hash, we can reorganize such that Raaz.Primitives.Hash from raaz-primitives,
Raaz.Hash.Test from the raaz-tests and Raaz.Hash package can now move
to the new raaz-hash package.