Extend `getBalance` request by adding support for `getCommittedAmount` parameter

[map1336]

Is your feature request related to a problem? Please describe.

Currently, the getAccount request has support for showing commitment balance.

Response example:

{
  "balanceNQT": "16143242542062",
  "unconfirmedBalanceNQT": "41616342062",
  "forgedBalanceNQT": "0",
  "guaranteedBalanceNQT": "16143242542062",
  "committedBalanceNQT": "16101626200000"
  // Remaining properties...
}

But the getBalance request does NOT have support for showing commitment balance.

Response example:

{
  "balanceNQT": "16143242542062",
  "unconfirmedBalanceNQT": "41616342062",
  "forgedBalanceNQT": "0",
  "guaranteedBalanceNQT": "16143242542062",
  "requestProcessingTime": 1
}

Describe the solution you'd like
The getBalance request must have support for that parameter also!

Describe alternatives you've considered
On the mobile wallet, i will be making the full request instead

Additional context
This request is lightweight compared to getAccount it allows any client to make more efficient queries.

[ohager]

Will consider this on current iteration...