Reading "HEAD" and "previous" from blockchains

[andrea-dintino]

In order to have a multilayer blockchain, for all the blockchains we support, we need statements that:

• read the HEAD of the blockchain
• given a certain "block", a statement that read the content of the previous block (I guess it's an address in Sawroom?)

Something like:

Given I read from Sawroom the data in the HEAD and save the output into 'sawroomHead'
Given I read from Sawroom the data in the address preceding 'myAddress' and save the output into 'sawroomPrevious'

Data:

{
"myAddress": "c274b51d3851ebcd31347fa373b4ca2e9be9eb0cadcc209f769af8156b9f754241013f"
}