Add mode, bring in definition/patch queries

src/Mode.php

@@ -0,0 +1,15 @@
+<?php declare(strict_types=1);
+
+namespace BitBadger\PDODocument;
+
+/**
+ * The mode for queries generated by the library
+ */
+enum Mode
+{
+    /** Storing documents in a PostgreSQL database */
+    case PgSQL;
+
+    /** Storing documents in a SQLite database */
+    case SQLite;
+}