Add Application Setting to configure default Repository Path for new projects

CHANGELOG

app/controllers/admin/application_settings_controller.rb

app/helpers/application_settings_helper.rb

app/models/application_setting.rb

app/models/project.rb

app/views/admin/application_settings/_form.html.haml

...4182521_add_repository_storage_to_application_settings.rb

db/schema.rb

doc/api/settings.md

lib/api/entities.rb

spec/models/application_setting_spec.rb

spec/models/project_spec.rb

spec/requests/api/settings_spec.rb