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.
Started working on Viewport concept for scrolling interfaces.
Add Content class to track a virtual cursor within the content of the interface.
Add #refresh method to update the interface after the cursor moves.
Use correct range operator to remove requirement to alter value of #viewport_height.
Return height with #attrs, also;

- Add temporary #width method.
- Add more documentation.
- Simplify movement.
Add options.
Add Area class.
Add options for Compositor to #by_name.
Add Viewport class.
Require Area and Viewport.
Add unused defaults.
Experimental stuff for scrolling, cursors and geometry.