Number of cards per list and sum of custom number field in list head.

Thanks to xet7 !

Fixes #3796

client/components/import/import.jade

@@ -1,7 +1,7 @@
 template(name="importHeaderBar")
   h1
     a.back-btn(href="{{pathFor 'home'}}")
-      i.fa.fa-chevron-left
+      | ⬅️
     | {{_ title}}
 
 template(name="import")
@@ -36,7 +36,7 @@ template(name="importMapMembers")
                 +userAvatar(userId=wekanId)
               else
                 a.member.add-member
-                  i.fa.fa-plus
+                  | ➕
         //-
           Due to the way the flewbox layout is working, we need to set some
           invisible items so that the last row items have a consistent width.