Simplified the CSS for issue boards

It gained a lot of extra cruft through the different improvements etc. This removes a lot of the stuff which would hopefully also speed up the browser rendering

app/assets/stylesheets/pages/boards.scss

@@ -18,6 +18,10 @@
   }
 }
 
+.is-ghost {
+  opacity: 0.3;
+}
+
 .dropdown-menu-issues-board-new {
   width: 320px;
 
@@ -34,47 +38,13 @@
   > p {
     margin: 0;
     font-size: 14px;
-    color: #9c9c9c;
   }
 }
 
 .issue-boards-page {
-  .content-wrapper {
-    display: -webkit-flex;
-    display: flex;
-    -webkit-flex-direction: column;
-    flex-direction: column;
-  }
-
-  .sub-nav,
-  .issues-filters {
-    -webkit-flex: none;
-    flex: none;
-  }
-
   .page-with-sidebar {
-    display: -webkit-flex;
-    display: flex;
-    min-height: 100vh;
-    max-height: 100vh;
     padding-bottom: 0;
   }
-
-  .issue-boards-content {
-    display: -webkit-flex;
-    display: flex;
-    -webkit-flex: 1;
-    flex: 1;
-    width: 100%;
-
-    .content {
-      display: -webkit-flex;
-      display: flex;
-      -webkit-flex-direction: column;
-      flex-direction: column;
-      width: 100%;
-    }
-  }
 }
 
 .boards-app-loading {
@@ -83,37 +53,29 @@
 }
 
 .boards-list {
-  display: -webkit-flex;
-  display: flex;
-  -webkit-flex: 1;
-  flex: 1;
-  -webkit-flex-basis: 0;
-  flex-basis: 0;
-  min-height: calc(100vh - 152px);
-  max-height: calc(100vh - 152px);
+  height: calc(100vh - 152px);
   padding-top: 25px;
+  padding-bottom: 25px;
   padding-right: ($gl-padding / 2);
   padding-left: ($gl-padding / 2);
   overflow-x: scroll;
+  white-space: nowrap;
 
   @media (min-width: $screen-sm-min) {
-    min-height: 475px;
-    max-height: none;
+    height: calc(100vh - 220px);
   }
 }
 
 .board {
-  display: -webkit-flex;
-  display: flex;
-  min-width: calc(85vw - 15px);
-  max-width: calc(85vw - 15px);
-  margin-bottom: 25px;
+  display: inline-block;
+  width: calc(85vw - 15px);
+  height: 100%;
   padding-right: ($gl-padding / 2);
   padding-left: ($gl-padding / 2);
+  white-space: normal;
 
   @media (min-width: $screen-sm-min) {
-    min-width: 400px;
-    max-width: 400px;
+    width: 400px;
   }
 }
 
@@ -123,6 +85,7 @@
   -webkit-flex-direction: column;
   flex-direction: column;
   width: 100%;
+  height: 100%;
   font-size: $issue-boards-font-size;
   background: $background-color;
   border: 1px solid $border-color;
@@ -193,45 +156,31 @@
 }
 
 .board-list {
-  -webkit-flex: 1;
-  flex: 1;
-  height: 400px;
+  height: 100%;
   margin-bottom: 0;
   padding: 5px;
+  list-style: none;
   overflow-y: scroll;
   overflow-x: hidden;
 }
 
 .board-list-loading {
   margin-top: 10px;
-  font-size: 26px;
-}
-
-.is-ghost {
-  opacity: 0.3;
+  font-size: (26px / $issue-boards-font-size) * 1em;
 }
 
 .card {
   position: relative;
-  width: 100%;
   padding: 10px $gl-padding;
   background: #fff;
   border-radius: $border-radius-default;
   box-shadow: 0 1px 2px rgba(186, 186, 186, 0.5);
   list-style: none;
 
-  &.user-can-drag {
-    padding-left: $gl-padding;
-  }
-
   &:not(:last-child) {
     margin-bottom: 5px;
   }
 
-  a {
-    cursor: pointer;
-  }
-
   .label {
     border: 0;
     outline: 0;
@@ -256,14 +205,13 @@
   line-height: 25px;
 
   .label {
-    margin-right: 4px;
+    margin-right: 5px;
     font-size: (14px / $issue-boards-font-size) * 1em;
   }
 }
 
 .card-number {
-  margin-right: 8px;
-  font-weight: 500;
+  margin-right: 5px;
 }
 
 .issue-boards-search {