Identify Input Payload Contracts

[dagurval]

Identifies and extract payload from Input Payload Contract.

We use this in VotePeer and we link to this explorer from the app. It would improve our app if this feature got accepted.

[dagurval]

Example transaction: 8df4ac34150d38e408356b2c516188c571d311cbcba355de4e5e1e5fdd494527

[sickpig]

@dagurval sorry for the delay in reviewing the PR (I must have missed the notification), the code looks good to me and I 'm ready to merge and deploy.

I just noticed that getInputPayloadContractPayload() used two different chars for indentation, 1 tab or 4 spaces for 1 indent level.

In the past I kept the same way of indenting as the upstream project we have forked from just to ahve an easier way to do backport when needed, but I wouldn't mind accepting the 4 spaces indenting style as long as the indention style is consistent.