Components should not be blueprint types.

[iago-lito]

Address this design mistake: blueprints and components should be two separate types hierarchies.

Using singleton component instances as ergonomical handles should improve #131.

Take this opportunity to better unify brought blueprint, either implied, embedded or unbrought depending on blueprint value.

This will surface as breaking API changes, but I expect them to remain minor. One major positive change I expect is the simplification of all code within src/components/: this should not become so complex than no one can hack in.