DS-2162: Per item configurable visual indicators for browse and search results (JSPUI only)

This is a rebase of #659 on master. Please, check #659 for some comments on previous PR.


JIRA Issue: https://jira.duraspace.org/browse/DS-2162

This PR adds per item visual indicators for browse and search results.

The extended functionality has the following specs:

1) Multiple marks can be added per item (i.e. mark the type of the item and the availability of the bitstreams) 
2) Easy configuration of the strategy of what mark to display in every item 
3) Marks based on images or a generic class (i.e. a glyphicon icon for bootstrap) 
4) Display tooltip when hovering the mark + localization of the tooltip 
5) Easy addtion of new strategies for any type of mark the user desires 
6) Add css styles for the user to configure the position of the marks in the list row

Documentation to follow!
This method is the same of org.dspace.app.webui.jsptag.ItemListTag.getMarkingMarkup(HttpServletRequest, Item, String). Please extract it and move to an utility class (for example org.dspace.app.webui.util.UIUtil). See the ItemListTag.getMarkingMarkup method to check other request change.