The use of OperandQP for public key is correct but a bit of an overkill, especially since public-keys
must be of size two (which requires an additional check at cast/read/write anyway) and because they
should not require to serialize ciphertext-related metadata.
Vector and Matrix now use []T and [][]T as underlying types, which makes them more versatile and easy to cast to from slices.
Map still uses map[K]V as map values cannot be addressed and this is anoying to use.
I also got rid of the Codec[T] type as it can be replaced with a 3-liner (i.e., equivalent to calling the Codex and checking the error).
There is also a small change of the OperendQ.Encode method that now uses OperandQ.WriteTo instead of OperandQ.Encode (since it is a bit fasterfor some reason...). This is an experiment and more work on the serialization is needed.
