Remove all gitlab theme related code

app/assets/javascripts/application.js

app/assets/stylesheets/framework.scss

app/assets/stylesheets/framework/animations.scss

app/assets/stylesheets/framework/gitlab-theme.scss

app/assets/stylesheets/framework/sidebar.scss

app/assets/stylesheets/pages/profiles/preferences.scss

app/helpers/preferences_helper.rb

app/views/layouts/application.html.haml

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

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

app/views/profiles/preferences/show.html.haml

app/views/profiles/preferences/update.js.erb

config/initializers/1_settings.rb

lib/gitlab/themes.rb

spec/features/profiles/preferences_spec.rb

spec/helpers/preferences_helper_spec.rb

spec/lib/gitlab/themes_spec.rb