Add getSchema action on framework

[shuse2]

Description

• Add getSchema action which returns schema below

getSchema: () => {
  account: {},
  blockHeader: {},
  blockHeadersAssets: { [version: number]: schema },
  baseTransaction: {},
  transactionsAssets: { [type: number}: schema },
}

Obtain block and account schema from the chain and transactions schema from registered transactions

• Update base plugin to register to app:ready event and call getSchema action there to cache schemas in the base plugin.

Motivation

When plugin receives encoded data through event or action, it needs to be able to decode it back in order to understand the content

Acceptance Criteria

• Add functional test for action and check if it returns the schemas