Add separate michelson/micheline representation in big-maps related data

[ivanopagano]

Block operations which include some code (like transactions) have a representation in conseil both in its original micheline format (as read from the tezos chain) and in converted michelson format, when successfully parsed.

The formats are mixed up in the same field for big maps and big maps content.

We might want to add a separate field there too to store the parsed michelson format.