修复seeder错误；删除第三方的think迁移工具，在extend中重新实现；

extend/phinx/Db/Action/DropIndex.php

@@ -0,0 +1,75 @@
+<?php
+
+/**
+ * MIT License
+ * For full license information, please view the LICENSE file that was distributed with this source code.
+ */
+
+namespace Phinx\Db\Action;
+
+use Phinx\Db\Table\Index;
+use Phinx\Db\Table\Table;
+
+class DropIndex extends Action
+{
+    /**
+     * The index to drop
+     *
+     * @var \Phinx\Db\Table\Index
+     */
+    protected $index;
+
+    /**
+     * Constructor
+     *
+     * @param \Phinx\Db\Table\Table $table The table owning the index
+     * @param \Phinx\Db\Table\Index $index The index to be dropped
+     */
+    public function __construct(Table $table, Index $index)
+    {
+        parent::__construct($table);
+        $this->index = $index;
+    }
+
+    /**
+     * Creates a new DropIndex object after assembling the passed
+     * arguments.
+     *
+     * @param \Phinx\Db\Table\Table $table The table where the index is
+     * @param string[] $columns the indexed columns
+     * @return static
+     */
+    public static function build(Table $table, array $columns = [])
+    {
+        $index = new Index();
+        $index->setColumns($columns);
+
+        return new static($table, $index);
+    }
+
+    /**
+     * Creates a new DropIndex when the name of the index to drop
+     * is known.
+     *
+     * @param \Phinx\Db\Table\Table $table The table where the index is
+     * @param string $name The name of the index
+     * @return static
+     */
+    public static function buildFromName(Table $table, string $name)
+    {
+        $index = new Index();
+        $index->setName($name);
+
+        return new static($table, $index);
+    }
+
+    /**
+     * Returns the index to be dropped
+     *
+     * @return \Phinx\Db\Table\Index
+     */
+    public function getIndex(): Index
+    {
+        return $this->index;
+    }
+}