Consistent, concise styling of datables

Add a semantic class to aggregate bootstrap classes and consistently
applyt them to all datatables.

app/views/admin/physical_tickets/index.html.haml

@@ -16,7 +16,7 @@
   - if @physical_tickets.any?
     .row
       .col-md-12
-        %table.table.table-hover.datatable#tickets
+        %table.datatable#tickets
           %thead
             %th ID
             %th Type