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.pdo/sparkplug.php

@@ -9,6 +9,7 @@ class PdoPlugin extends SparkPlug {
     {
         register_command(new Commands\PdoQueryCommand());
         register_command(new Commands\PdoExecCommand());
+        register_command(new Commands\PdoInspectCommand());
     }
 }