Rename activity to project tab

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

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

 %ul.project-navigation
   = nav_link(path: 'projects#show', html_options: {class: "home"}) do
     = link_to project_path(@project), title: 'Project', class: 'shortcuts-activity' do
-      Activity
+      Project
   - if project_nav_tab? :files
     = nav_link(controller: %w(tree blob blame edit_tree new_tree)) do
       = link_to 'Files', project_tree_path(@project, @ref || @repository.root_ref), class: 'shortcuts-tree'

features/steps/shared/project_tab.rb

@@ -3,7 +3,7 @@ module SharedProjectTab
   include SharedActiveTab
 
   step 'the active main tab should be Home' do
-    ensure_active_main_tab('Activity')
+    ensure_active_main_tab('Project')
   end
 
   step 'the active main tab should be Files' do