[NFR]: Hint for commands that a package provides

[niden]

Goal: tell the user which package provides an unknown command.

Without phalcon/migrations installed, crest migration:run prints:

unknown command 'migration:run'

The user does not learn that a package provides the command. Proposed:

unknown command 'migration:run'; provided by phalcon/migrations

• A prefix-to-package map in Crest\Commands, for example migration: to phalcon/migrations. Strings only, no class references, so nothing breaks when a package changes its classes.
• The console core gets the map from outside, for example as a constructor argument. Crest\Console must not name crest or its packages (IsolationTest). The error comes from Registry (src/Console/Registry.php).
• Tests: the hint prints for a known prefix, and the plain message stays for every other name.

This needs no change in phalcon/migrations. It does not depend on [NFR]: Package-contributed commands.

[niden]

Resolved in #25