Information for a users achievement.
This defines the relation between a particular achievement (described by
IAchievementDescription) and the local user, what progress he has, last date he reported progress and so on.
Use Social.CreateAchievement to create an instance of this object.
| completed | Set to true when percentCompleted is 100.0. |
| hidden | This achievement is currently hidden from the user. |
| id | The unique identifier of this achievement. |
| lastReportedDate | Set by server when percentCompleted is updated. |
| percentCompleted | Progress for this achievement. |
| ReportProgress | Send notification about progress on this achievement. |