UI: add new button, top panel restyle etc

app/assets/images/Arrow-Left-UI.PNG

app/assets/images/Gear-UI.PNG

app/assets/images/Home-UI.PNG

app/assets/images/Info-UI.PNG

app/assets/images/Rss-UI.PNG

app/assets/images/add_new.png

app/assets/images/rss_icon_gray.png

app/assets/stylesheets/projects.css.scss

app/assets/stylesheets/style.scss

app/assets/stylesheets/top_panel.scss

app/assets/stylesheets/tree.scss

app/controllers/help_controller.rb

app/helpers/application_helper.rb

app/views/commits/index.html.haml

app/views/help/index.html.haml

app/views/issues/_head.html.haml

app/views/issues/index.html.haml

app/views/layouts/_head_panel.html.haml

app/views/merge_requests/_head.html.haml

app/views/merge_requests/index.html.haml