Move group settings navigation to own partial

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

app/views/layouts/nav/_group.html.haml

-- if current_user
-  - if access = @group.users.find_by(id: current_user.id)
-    .controls
-      %span.dropdown.group-settings-dropdown
-        %a.dropdown-new.btn.btn-gray#group-settings-button{href: '#', 'data-toggle' => 'dropdown'}
-          = icon('cog')
-          = icon('caret-down')
-        %ul.dropdown-menu.dropdown-menu-align-right
-          - if can?(current_user, :admin_group, @group)
-            = nav_link(path: 'groups#projects') do
-              = link_to projects_group_path(@group), title: 'Projects' do
-                Projects
-            %li.divider
-            %li
-              = link_to edit_group_path(@group) do
-                Edit Group
-          %li
-            = link_to leave_group_group_members_path(@group),
-              data: { confirm: leave_group_message(@group.name) }, method: :delete, title: 'Leave group' do
-              Leave Group
+= render 'layouts/nav/group_settings'
 %ul.nav-links
   = nav_link(path: 'groups#show', html_options: {class: 'home'}) do

app/views/layouts/nav/_group_settings.html.haml

-%ul.nav.nav-sidebar
-  = nav_link do
-    = link_to group_path(@group), title: 'Go to group', class: 'back-link' do
-      = icon('caret-square-o-left fw')
-      %span
-        Go to group
-
-  %li.separate-item
-
-  %ul.sidebar-subnav
-    = nav_link(path: 'groups#edit') do
-      = link_to edit_group_path(@group), title: 'Group Settings' do
-        = icon ('pencil-square-o fw')
-        %span
-          Group Settings
-    = nav_link(path: 'groups#projects') do
-      = link_to projects_group_path(@group), title: 'Projects' do
-        = icon('folder fw')
-        %span
-          Projects
+- if current_user
+  - if access = @group.users.find_by(id: current_user.id)
+    .controls
+      %span.dropdown.group-settings-dropdown
+        %a.dropdown-new.btn.btn-gray#group-settings-button{href: '#', 'data-toggle' => 'dropdown'}
+          = icon('cog')
+          = icon('caret-down')
+        %ul.dropdown-menu.dropdown-menu-align-right
+          - if can?(current_user, :admin_group, @group)
+            = nav_link(path: 'groups#projects') do
+              = link_to projects_group_path(@group), title: 'Projects' do
+                Projects
+            %li.divider
+            %li
+              = link_to edit_group_path(@group) do
+                Edit Group
+          %li
+            = link_to leave_group_group_members_path(@group),
+              data: { confirm: leave_group_message(@group.name) }, method: :delete, title: 'Leave group' do
+              Leave Group