Add #all to Buffers, Cursors and Focus for consistency.

Conflicts:
	lib/vedeu/repositories/cursors.rb
Update minitest and simplecov versions.
Convert Events into a repository module;

- Remove #events from API.
Move methods to Repository;

- #all
- #find
- #registered
- #registered?
- #reset
Remove duplication.
Fix typo in event name.
Add more documentation.
Improve Trace;

- Move trace call as not all classes were loaded at this point.
- Don't log the event as most of the time it is one value (by default, 'call').
- Colourize primitive classes.
- Add argument class inspection.
- Separate and ignore exception classes.
- Add ignored classes list to decrease verbosity.
- Don't trace API#log.