`"validateaddress"` omits some information, even in cases where is it available.

The primary motivation is to be able to retrieve redeemScripts, after using `"addmultisigaddress"`, when not all keys are available in the keystore, but the redeemScript actually is.

The output of `"validateaddress"` with this commit:

Keys not available:
```js
validateaddress "n4KWZKx349gdMQGgTnZ8W6WfgSwybkGSK3"
{
  "isvalid": true,
  "address": "n4KWZKx349gdMQGgTnZ8W6WfgSwybkGSK3",
  "scriptPubKey": "76a914fa20d564550b105787f7ce3a9ad7fd9a45cd407088ac",
  "ismine": false,
  "iswatchonly": false,
  "isscript": false
}
```
```js
validateaddress "2N2g2H7gjA8a11g1yKBgh5VTqndyvbnWpBK"
{
  "isvalid": true,
  "address": "2N2g2H7gjA8a11g1yKBgh5VTqndyvbnWpBK",
  "scriptPubKey": "a9146769c19a16c9400b908756e19a4d2afb9e9760e187",
  "ismine": false,
  "iswatchonly": false,
  "isscript": true
}
```

After adding the redeemScript:
```js
addmultisigaddress 2 '["02537357B156A33306A7A014A3748631C59DF405B56F11BA4AA4A3CE81501AF095","02F1FB200390E7864EF4450C07B15988179A57C3CF3A878F668E1070CB615749FE"]'
2N2g2H7gjA8a11g1yKBgh5VTqndyvbnWpBK

validateaddress "2N2g2H7gjA8a11g1yKBgh5VTqndyvbnWpBK"
{
  "isvalid": true,
  "address": "2N2g2H7gjA8a11g1yKBgh5VTqndyvbnWpBK",
  "scriptPubKey": "a9146769c19a16c9400b908756e19a4d2afb9e9760e187",
  "ismine": false,
  "iswatchonly": false,
  "isscript": true,
  "script": "multisig",
  "hex": "522102537357b156a33306a7a014a3748631c59df405b56f11ba4aa4a3ce81501af0952102f1fb200390e7864ef4450c07b15988179a57c3cf3a878f668e1070cb615749fe52ae",
  "addresses": [
    "n4KWZKx349gdMQGgTnZ8W6WfgSwybkGSK3",
    "mmSKNtbYYHRrhTLKiok5TuYrGEs4Y2A4k6"
  ],
  "sigsrequired": 2,
  "account": ""
}
```

All keys available:
```js
validateaddress "n4KWZKx349gdMQGgTnZ8W6WfgSwybkGSK3"
{
  "isvalid": true,
  "address": "n4KWZKx349gdMQGgTnZ8W6WfgSwybkGSK3",
  "scriptPubKey": "76a914fa20d564550b105787f7ce3a9ad7fd9a45cd407088ac",
  "ismine": true,
  "iswatchonly": false,
  "isscript": false,
  "pubkey": "02537357b156a33306a7a014a3748631c59df405b56f11ba4aa4a3ce81501af095",
  "iscompressed": true,
  "account": ""
}
```
```js
validateaddress "2N2g2H7gjA8a11g1yKBgh5VTqndyvbnWpBK"
{
  "isvalid": true,
  "address": "2N2g2H7gjA8a11g1yKBgh5VTqndyvbnWpBK",
  "scriptPubKey": "a9146769c19a16c9400b908756e19a4d2afb9e9760e187",
  "ismine": true,
  "iswatchonly": false,
  "isscript": true,
  "script": "multisig",
  "hex": "522102537357b156a33306a7a014a3748631c59df405b56f11ba4aa4a3ce81501af0952102f1fb200390e7864ef4450c07b15988179a57c3cf3a878f668e1070cb615749fe52ae",
  "addresses": [
    "n4KWZKx349gdMQGgTnZ8W6WfgSwybkGSK3",
    "mmSKNtbYYHRrhTLKiok5TuYrGEs4Y2A4k6"
  ],
  "sigsrequired": 2,
  "account": ""
}
```