Allow SmartEvidence use custom status icons

[Robert Lyon]

Currently we allow SmartEvidence matrix files to define custom status settings for the 4 statuses

But we don't allow for custom icons relating to those statuses.

It would be good if we also allowed / recorded what icon to use for the status

This would entail
1) being able to define it in the matrix file, eg

     "evidencestatusesicons":
      [
        {"begun":"icon-square"},
        {"incomplete":"icon-triangle"},
        {"partialcomplete":""},
        {"completed":"icon-star"}
      ],

We'd also need to handle stacked icons, where we can stack icons on top of each other
See http://fontawesome.io/examples/ the stacked icon section

So we could do this by allowing an array {"completed":["icon-circle","icon-star"]}

2) Save the icon info in the framework_evidence_statuses table by adding a icon column. We can save the data in json format to make things easier to keep the 1 to 1 connection between status and the icon(s) to use.

3) Being able to define the icon in html by using a matrix-icon.tpl file where we can define the markup allowing if/else checks so we return the correct markup for normal vs stacked icons and fetch it via smarty

4) In get_statuses_to_display() we fetch the html via template and add the html to the array. So rather that setting 'classes' we set 'iconhtml' and pass that to the matrix template.