Websockets support for API

[erik-iglikov]

I'm running:

• Which Aion version?: v0.3.2 - Ama Dablam
• Which operating system?: any
• Which distributor and version?: any
• How installed?: any
• Are you fully synchronized?: N/A
• Did you try to restart the node?: N/A

Your issue description goes here below. Try to include actual vs. expected behavior and steps to reproduce the issue.

We've been receiving a lot of requests for websockets support in our API.

Functions that have been requested:
eth_blockNumber
eth_call
eth_getBalance
eth_getBlockByNumber
eth_getLogs
eth_getTransactionCount
eth_getTransactionReceipt
eth_sendRawTransaction

Details:
Significant amount of developers have been requesting WebSockets functionality for functions that are inherently dependent on long polling (events, receipts, blocks)