add directive attribute to bind the component focus

[rafaelhz]

Add possibility to set the component initial state focused, and allow set focus by another component

Examples:
binding the property:

<nit-advanced-searchbox
  set-search-focus="searchFocus">
</nit-advanced-searchbox>
<a ng-click="searchFocus = true">Set Focus</a>

just setting the initial state focused

<nit-advanced-searchbox
  set-search-focus="true">
</nit-advanced-searchbox>