Ability to retrieve data source info

I have added a <code>/DataSource</code> route and suitable methods to retreve data source information. Also I have changed <code>GetWidgetsList</code> method so that in a list of widgets will appear <code>dataSource</code> property, that can be passed to <code>/DataSource</code> requests.

Example: request to <code>http://localhost:57772/samples/DataSource</code> with data
```js
{
	DataSource:"KPIs & Plugins/HoleFoods.pivot"
}
```
will return something like
```js
{
	"_class":"%DeepSee.Dashboard.Pivot",
	"_id":25,
	"name":"HoleFoods",
	"folder": {
		"_class":"%DeepSee.UserLibrary.Folder",
		"_id":4,
		"fullName":"KPIs & Plugins",
		"name":"KPIs & Plugins",
		"folder":null,
		"items":[],
		"resource":""
	},
	"folderName":"KPIs & Plugins",
	"fullName":"KPIs & Plugins\/HoleFoods.pivot",
	"documentName":"KPIs & Plugins-HoleFoods.pivot.DFI",
	"title":"",
	"description":"",
	"keywords":"HoleFoods,Plugin",
	"owner":"",
	"shared":true,
	"public":false,
	"locked":false,
	"resource":"",
	"timeCreated":"2013-01-07 22:48:41.31",
	"timeModified":"2014-06-06 21:16:34.487",
	"...": "...",
	"showStatus":true,
	"rowAxisOptions": { "...": "..." },
	"...": "..."
}
```

This is important for my [light pivot table project](https://github.com/ZitRos/LightPivotTable), because I can examine all source settings, such as custom drillDown specs.