[Slim] Improve codebase decouple (#438)

* [Slim] Decouple Api files into separated PHP Classes

This enhancement required for modular testing and code coverage generating.

* [Slim] Define all app routes in SlimRouter PHP Class. Generate new samples

samples/server/petstore/php-slim/lib/Model/MapTest.php

@@ -0,0 +1,24 @@
+<?php
+/**
+ * MapTest
+ */
+namespace OpenAPIServer\Model;
+
+/**
+ * MapTest
+ */
+class MapTest {
+
+    /** @var map[string,map[string,string]] $mapMapOfString */
+    private $mapMapOfString;
+
+    /** @var map[string,string] $mapOfEnumString */
+    private $mapOfEnumString;
+
+    /** @var map[string,bool] $directMap */
+    private $directMap;
+
+    /** @var \OpenAPIServer\Model\StringBooleanMap $indirectMap */
+    private $indirectMap;
+
+}