PDO plugin: Reflections

* com.noccy.pdo: Implemented reflection for PDO databases,
  tables and columns. Reflectors for MySQL and Sqlite.
* com.noccy.pdo: Added pdo:inspect command.
* com.noccy.docker: Added basic stack management and commands.
* com.noccy.docker: Moved commands to dedicated namespace.
* Environment: readConfig and writeConfig helper added, with
  a flag to use the global config dir ~/.config/spark.

plugins/com.noccy.docker/Commands/DockerBuildCommand.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace SparkPlug\Com\Noccy\Docker\Commands;
+
+use Spark\Commands\Command;
+use SparkPlug;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+class DockerBuildCommand extends Command
+{
+    protected function configure()
+    {
+        $this->setName("docker:build")
+            ->setDescription("Build an image");
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output)
+    {
+        $config = read_config("docker.json");
+        print_r($config);
+        return Command::SUCCESS;
+    }
+}