Add functions documentation
Name fixes

- Fix app_id parameter name for update_application_manifest
- Fix instance_id parameter name for launch_workflow
- Fix workflow parameters description for launch_workflow
Improve return types definitions
Documentation improves

- Add top-level class documentation
- Add class attributes description
- Fix endpoint parameter description length
Fix return value description for qubell_request method
Merge branch 'docs' into dev

Conflicts:
	lib/qubell_api.rb