Added Documentation for esri Namespace

Added documentation for these classes:
- esriRequest
- domUtils
- esriLang
- ProxyRule
- urlUtils
- Credential
- Graphic
- IdentityManagerBase
- IdentityManager
- InfoTemplate
- InfoWindowBase
- OperationBase
- Map
- ServerInfo
- SnappingManager
- SpatialReference
- TimeExtent
- UndoManager
- Units