Fix and complement .gitignore file.
Add events mechanism dependencies to setup.py file.
Add protobuf definition for events messages and services.
Add a server for events mechanism.
Add support for components in events mechanism.
Add events module with basic API.
Add tests for events mechanism.
Add README and changes file for events mechanism.
Merge remote-tracking branch 'drebs/feature/events-signals' into develop

Conflicts:
	.gitignore
	src/leap/common/__init__.py