Swimlanes collapsed by default.

TODO:
- Add count.
- Move list names to top, if possible. I did not get it working yet.
- Try to fit collapse+swimlane name etc at same row.

Related #2804

client/components/swimlanes/swimlanes.jade

@@ -1,24 +1,27 @@
 template(name="swimlane")
   .swimlane
     +swimlaneHeader
-  .swimlane.js-lists.js-swimlane
-    if isMiniScreen
-      if currentListIsInThisSwimlane _id
-        +list(currentList)
-      unless currentList
+  // Minimize swimlanes next 2 lines below https://www.w3schools.com/howto/howto_js_accordion.asp
+  button(class="accordion")
+  div(class="panel")
+    .swimlane.js-lists.js-swimlane
+      if isMiniScreen
+        if currentListIsInThisSwimlane _id
+          +list(currentList)
+        unless currentList
+          each lists
+            +miniList(this)
+          if currentUser.isBoardMember
+            unless currentUser.isCommentOnly
+              +addListForm
+      else
         each lists
-          +miniList(this)
+          +list(this)
+          if currentCardIsInThisList _id ../_id
+            +cardDetails(currentCard)
         if currentUser.isBoardMember
           unless currentUser.isCommentOnly
             +addListForm
-    else
-      each lists
-        +list(this)
-        if currentCardIsInThisList _id ../_id
-          +cardDetails(currentCard)
-      if currentUser.isBoardMember
-        unless currentUser.isCommentOnly
-          +addListForm
 
 template(name="listsGroup")
   .swimlane.list-group.js-lists

client/components/swimlanes/swimlanes.js

@@ -134,6 +134,22 @@ BlazeComponent.extendComponent({
     }
 
     initSortable(boardComponent, $listsDom);
+
+    // Minimize swimlanes start https://www.w3schools.com/howto/howto_js_accordion.asp
+    var acc = document.getElementsByClassName("accordion");
+    var i;
+    for (i = 0; i < acc.length; i++) {
+      acc[i].addEventListener("click", function() {
+        this.classList.toggle("active");
+        var panel = this.nextElementSibling;
+        if (panel.style.maxHeight) {
+          panel.style.maxHeight = null;
+        } else {
+          panel.style.maxHeight = panel.scrollHeight + "px";
+        }
+      });
+    }
+    // Minimize swimlanes end https://www.w3schools.com/howto/howto_js_accordion.asp
   },
   onCreated() {
     this.draggingActive = new ReactiveVar(false);

client/components/swimlanes/swimlanes.styl

@@ -1,5 +1,39 @@
 @import 'nib'
 
+// Minimize swimlanes start https://www.w3schools.com/howto/howto_js_accordion.asp
+
+.accordion
+  cursor: pointer
+  width: 30px
+  height: 20px
+  border: none
+  outline: none
+  font-size: 18px
+  transition: 0.4s
+  padding-top: 0px
+  margin-top: 0px
+
+.accordion:after
+  // Unicode triagle right:
+  content: '\25B6'
+  color: #777
+  font-weight: bold
+  float: left
+
+.active:after
+  // Unicode triangle down:
+  content: '\25BC'
+
+.panel
+  width: 100%
+  max-height: 0
+  overflow: hidden
+  transition: max-height 0.2s ease-out
+  margin: 0px
+  padding: 0px
+
+// Minimize swimlanes end https://www.w3schools.com/howto/howto_js_accordion.asp
+
 .swimlane
   // Even if this background color is the same as the body we can't leave it
   // transparent, because that won't work during a swimlane drag.
@@ -25,22 +59,22 @@
       cursor: grabbing
 
   .swimlane-header-wrap
-    display: flex;
-    flex-direction: row;
-    flex: 1 0 100%;
-    background-color: #ccc;
+    display: flex
+    flex-direction: row
+    flex: 1 0 100%
+    background-color: #ccc
 
     .swimlane-header
-      font-size: 14px;
+      font-size: 14px
       padding: 5px 5px
-      font-weight: bold;
-      min-height: 9px;
-      width: 100%;
-      overflow: hidden;
-      -o-text-overflow: ellipsis;
-      text-overflow: ellipsis;
-      word-wrap: break-word;
-      text-align: center;
+      font-weight: bold
+      min-height: 9px
+      width: 100%
+      overflow: hidden
+      -o-text-overflow: ellipsis
+      text-overflow: ellipsis
+      word-wrap: break-word
+      text-align: center
 
     .swimlane-header-menu
       position: absolute