Add lastLogin to user REST API

To help with administration, it'd be helpful to have the lastLogin property of a user exposed through the REST interface.

Example, when calling /rest/api/2/user?username, the response would include lastLogin:

{
"self": "http://www.example.com/jira/rest/api/2/user?username=fred",
"name": "fred",
"emailAddress": "fred@example.com",
"avatarUrls":

{ "24x24": "http://www.example.com/jira/secure/useravatar?size=small&ownerId=fred", "16x16": "http://www.example.com/jira/secure/useravatar?size=xsmall&ownerId=fred", "32x32": "http://www.example.com/jira/secure/useravatar?size=medium&ownerId=fred", "48x48": "http://www.example.com/jira/secure/useravatar?size=large&ownerId=fred" }

,
"displayName": "Fred F. User",
"active": true,
"timeZone": "Australia/Sydney",
"lastLogin": "2011-07-05T11:05:00.000+0000"
"groups": {
"size": 3,
"items": [

{ "name": "jira-user", "self": "http://www.example.com/jira/rest/api/2/group?groupname=jira-user" }

,

{ "name": "jira-admin", "self": "http://www.example.com/jira/rest/api/2/group?groupname=jira-admin" }

,

{ "name": "important", "self": "http://www.example.com/jira/rest/api/2/group?groupname=important" }

]
},
"expand": "groups"
}