feature: return transfers and fees count on acocunt detail

[selankon]

Describe the feature

Add transfers and fees count when retrieving account detail

Motivation

To avoid additional calls on the explorer, a transfers and fees count could be added when calling account detail count. On this way, we could show this information on the account detail page, without retrieving the first page of the list.

Proposal

Api should return something like:

➜ curl 'https://api-dev.vocdoni.net/v2/accounts/94ec63c0c708a3b77fc7358ccd90a31f27ff2c4f' -s | jq                                                                                      
{
  "address": "94ec63c0c708a3b77fc7358ccd90a31f27ff2c4f",
  "nonce": 1,
  "balance": 9995,
  "electionIndex": 1,
  "transfers": 1,
  "fees": 1,
//...
}