Add cache option to ngRepeat to keep filtered out DOM element

Add keepCache parameter to have the option to keep in a cache and hide DOM elements associated to filtered out object of the collection. Make it faster to display again those element when filtered in.

For a large collection, it is sometimes very slow for angular to recreate all DOM node that were filtered out and are now filtered in. This prevent the deletion of those DOM nodes and keep them in a cache. 

Usage: 

<div ng-repeat="period in tL.filteredTransactions"  keep-cache="true" >