Inter-operable between Java RS erasure coder and native RS erasure coder

It's natural and desired to support inter-operable between the two implemented RS raw erasure coders, in other words, data encoded in one coder (like RSRawEncoder) can be decoded using the other coder (like NativeRSRawDecoder). Without this, raw erasure coder will not be transparent to HDFS data. As such support isn't trivial and involves challenge work because the two implementations use different encode/decode matrix generation algorithms, better to have this separately.