Add hideSelectionFromResult function

Update to PR #2032: transform `hideSelectionFromResult` property into a function that the user can implement for single and multi select boxes. 

For instance, a basic example to remove the selected item from the result list inside a single select boxes:

![hideselectionfromresultsingle](https://f.cloud.github.com/assets/369777/1951526/cd16acb8-8182-11e3-950a-02c891c36652.png)

In the case of a multi select box, `hideSelectionFromResult` could be used to allow the same item to be selected more than once.