User preview card: add an id attribute to make it easier to write functional tests

add an id attribute to make it easier to write functional tests

What is the current behavior?

<li class="col-xs-12 col-sm-6 col-md-3 col-lg-3">
     <div class="user-unit-home backgroundUnit list-unstyled">
          <a href="/users/57" class="linkItem linkItemAllArea"> (...

What is the expected *correct *behavior?

<li class="col-xs-12 col-sm-6 col-md-3 col-lg-3">
     <div class="software-unit-home backgroundUnit" id="userPreviewCard-10"> 
(...)
     <div class="size-logo">
          <a href="/softwares/10" title="Software name : LUTECE"> (...)