Elastic plugin : Initial revision

Elastic plugin take the children of an element and rearrange them in a grid layout (like google+ or pinterest)

To call the plugin: 
```java
import static com.arcbees.gquery.elastic.client.Elastic.Elastic;

ElasticOption option = new ElasticOption()
           .withColumWidth(400)
           .withMinimalNumberOfColumn(2);

            $("#container").as(Elastic).elastic(option);
```

The different options:
* _columnWidth_: Specify the minimum width of the column. The plugin uses this value to maximise the 
number of column to display. (default: 250px)
* _minimalNumberOfColumn_: Specify the minimum number of column. (default: 1)
* _maximumNumberOfColumn_: Specify the maximum number of column. (default: infinity)
* _maximumNumberOfColumn_: Specify the maximum number of column. (default: infinity)
* _InnerColumnMargin_: Specify the space between each column (default: 10px)
* _InnerRowMargin_: Specify the space between each row (default: 10px)
*_autoResize_: Specify if we have to recalculate the layout after a window resizing. (default: true)

On each child we can specify the following attributes:
*_data-elastic-span_: specify the number of column to span for this child.
*_data-elastic-column_: Force the child to be displayed in a specific column. "first" and "last" values are also accepted and the child will be displayed respectively in the first of in the last column no matter the number of column