Dashboard: display index queue

[jamiehewitt15]

Fixes #290

Changes proposed in this PR:

• The dashboard now shows the indexing queue:
  

To Test:

1. npm run build && npm run start

2. Add a transaction to the indexing queue. send a POST request to the direct command endpoint: http://127.0.0.1:8000/directCommand

Example body:

{
    "command": "reIndex",
    "chainId": 137,
    "txId": "0xc53ba79bdcdba60c466c401631edc97383c230e1fdd1a734737cdab033446923"
}

3. You should see the transaction appear in the indexing queue on the dashboard.

[paulo-ocean]

LGTM!
not really sure if we should poll the queue every 2 seconds, might be too much

[bogdanfazakas]

lgt, just one small suggestion but not mandatory