Code improvements and add Create group service

app/assets/stylesheets/framework/common.scss

app/assets/stylesheets/framework/mobile.scss

app/assets/stylesheets/pages/projects.scss

app/controllers/groups_controller.rb

app/controllers/users_controller.rb

app/finders/joined_groups_finder.rb

app/models/ability.rb

app/services/groups/base_service.rb

app/services/groups/create_service.rb

app/services/groups/update_service.rb

app/services/projects/create_service.rb

app/views/groups/show.html.haml

app/views/projects/_home_panel.html.haml

...3_add_default_group_visibility_to_application_settings.rb

db/schema.rb

spec/features/security/group/internal_access_spec.rb

spec/services/groups/create_service_spec.rb