Add group avatar to group page. Changed default avatar for group

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/views/dashboard/_groups.html.haml

@@ -10,7 +10,7 @@
     - groups.each do |group|
       %li.group-row
         = link_to group_path(id: group.path), class: dom_class(group) do
-          = image_tag group_icon(group.path), class: "avatar s32"
+          = image_tag group_icon(group.path), class: "avatar s24"
           %span.group-name.filter-title
             = truncate(group.name, length: 35)
           %span.arrow

app/views/groups/show.html.haml

@@ -13,9 +13,13 @@
       %p.nothing_here_message Project activity will be displayed here
     .loading.hide
   .side.col-md-4
-    - if @group.description.present?
-      .description-block
-        = @group.description
+    .light-well.append-bottom-20
+      = image_tag group_icon(@group.path), class: "avatar s90"
+      .clearfix.light
+        %h3.page-title
+          = @group.name
+        - if @group.description.present?
+          %p= @group.description
     = render "projects", projects: @projects
     .prepend-top-20
       = link_to group_path(@group, { format: :atom, private_token: current_user.private_token }), title: "Feed" do