public static long toLong(byte[] bytes, int offset) {
        return toLong(bytes, offset, SIZEOF_LONG);
    }
Converts a byte array to a long value. Assumes there will be {@link #SIZEOF_LONG} bytes
available.

@param bytes  bytes
@param offset offset
@return the long value
stroom-bytebuffer/src/main/java/stroom/bytebuffer/hbase/Bytes.java