Expand Blueprint into DatabaseBlueprint, SchemaBlueprint, and TableBlueprint

[AdamLenda]

These changes extend the work that was done in https://github.com/reliese/laravel/pull/200/files

The new classes define a (hopefully) "idealized" representation of meta data from a database.

In the case of SchemaBlueprint it is a wrapper around a the existing Schema implementations.

The reason it is implemented as a "wrapper" is to ensure that previous implementations can be "adapted" to fit a new object model that organizes blueprints as a hierarchy of blueprints.

intended usage:

    public function handle()
    {
        $connection = $this->getConnection();
        $schema = $this->getSchema($connection);
        $table = $this->getTable();

        $schemaBlueprint = $this->blueprintFactory->database($connection)->schema($schema);

        $tableBlueprints = [];
        // Check whether we just need to generate one table
        if ($table) {
            $tableBlueprints[] = $schemaBlueprint->table($table);
        } else {
            $tableBlueprints = $schemaBlueprint->allTables($table);
        }
        
        /* TODO: allow command options to override the blueprint definition */

        // convert Blueprints into Model definitions
        $modelManager = new ModelManager($config);
        foreach ($tableBlueprints as $tableBlueprint) {
            $model = $this->modelFactory->fromTableBlueprint($tableBlueprint);
            $modelManager->addModel($model);
        }
        
        $modelManager->generateModelFiles();
        
    }

[CristianLlanos]

Even though PHP might work this way, we should give an initial value to our variables.

Suggested change

	private $schemaBlueprints;
	private $schemaBlueprints = [];