Remove bus from chain module

[shuse2]

Expected behavior

Since we introduced the new architecture supporting the inter-module communication through the channels, we should use them to facilitate the interactions within the chain modules itself.

Actual behavior

To communicate between modules we use the bus (as a helper).

Steps to reproduce

• the bus helper is removed
• the bus usages are replaced by channel.invoke calls

Which version(s) does this affect? (Environment, OS, etc...)

*

[lsilvs]

Also, consider replacing the use of EventEmitter as extended class.

Current extended by:

framework/src/modules/chain/blocks/blocks.js
framework/src/modules/chain/transaction_pool/transaction_pool.js