message: NodeJs Sample revocation : add explanations to script + small refactoring
diff: +/**
  + * This script is a sample to show revocation process.
  + *
  + * Scenario :
  + * - Issuer create schema, credential definition, revocation registry and revocation registry entry
  + * - Issuer create and send offer to prover
  + * - Prover request credential
  + * - Issuer issues credential to prover
  + * - Verifier create proof request
  + * - Prover search credential and create proof, with revocation state
  + * - Verifier gets revocation data, and verifies proof is non-revoked (--> true)
  + * - Issuer revoke credential and posts delta to ledger
  + * - Verifier gets delta from ledger (until now), and verifies that proof is revoked (false)
  + * - Verifier gets delta from ledger until proof reception timestamp, and verifies that proof at this timestamp is non-revoked
  + *
  + * All logs are colored differently for each actor (cyan for issuer, magenta for prover and yellow for verifier).
  + * Data checked as expected are logged with green color, otherwise the logs are red.
  + *
  + * To ensure that there is no data shared with local variables between each actors, all data are stored in
  + * separated spaces (issuer = {}, prover = {}, verifier = {}). Likewise, some instructions with local variables
  + * are grouped in "blocks" ( {...} ) to avoid involuntary data sharing between actors.
  + */
  +
  const indy = require('indy-sdk')
  const util = require('./util')
  const COLOR = require('./colors')
  @@ -307,12 +330,16 @@ async function run() {
  prover.searchHandle = await indy.proverSearchCredentialsForProofReq(prover.wallet, prover.proofReq, undefined)
  logProver("Prover gets Credentials for attr1_referent")
  + {
  const credentialsForAttr1 = await indy.proverFetchCredentialsForProofReq(prover.searchHandle, 'attr1_referent', 10)
  - const credInfoForAttribute = credentialsForAttr1[0]['cred_info']
  + prover.credInfoForAttribute = credentialsForAttr1[0]['cred_info']
  + }
  logProver("Prover gets Credentials for predicate1_referent")
  + {
  const credentialsForPredicate1 = await indy.proverFetchCredentialsForProofReq(prover.searchHandle, 'predicate1_referent', 10)
  - const credInfoForPredicate = credentialsForPredicate1[0]['cred_info']
  + prover.credInfoForPredicate = credentialsForPredicate1[0]['cred_info']
  + }
  await indy.proverCloseCredentialsSearchForProofReq(prover.searchHandle)
  @@ -330,7 +357,7 @@ async function run() {
  }
  logProver("Prover creates revocation state")
  - prover.credRevId = credInfoForAttribute['cred_rev_id']
  + prover.credRevId = prover.credInfoForAttribute['cred_rev_id']
  prover.revState = await indy.createRevocationState(prover.blobStorageReaderHandle, prover.revRegDef, prover.revRegDelta, prover.timestampOfDelta, prover.credRevId)
  logProver("Prover Gets Schema from Ledger")
  @@ -341,11 +368,11 @@ async function run() {
  'self_attested_attributes': {},
  'requested_attributes': {
  'attr1_referent': {
  - 'cred_id': credInfoForAttribute['referent'], 'revealed': true, 'timestamp': prover.timestampOfDelta
  + 'cred_id': prover.credInfoForAttribute['referent'], 'revealed': true, 'timestamp': prover.timestampOfDelta
  }
  },
  'requested_predicates': {
  - 'predicate1_referent': {'cred_id': credInfoForPredicate['referent'], 'timestamp': prover.timestampOfDelta}
  + 'predicate1_referent': {'cred_id': prover.credInfoForPredicate['referent'], 'timestamp': prover.timestampOfDelta}
  }
  }
  prover.schemas = {
  