[php] Fix null+required properties to accept null values in generated models. Also fix PHP annotations related to same.

Author: achton

modules/openapi-generator/src/main/resources/php/model_generic.mustache

@@ -284,7 +284,7 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}}{{/parentSchema}}{{^par
 
         {{#vars}}
         {{#required}}
-        if ($this->container['{{name}}'] === null) {
+        if ($this->container['{{name}}'] === null{{#isNullable}} && !$this->isNullableSetToNull('{{name}}'){{/isNullable}}) {
             $invalidProperties[] = "'{{name}}' can't be null";
         }
         {{/required}}
@@ -365,7 +365,7 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}}{{/parentSchema}}{{^par
     /**
      * Gets {{name}}
      *
-     * @return {{{dataType}}}{{^required}}|null{{/required}}
+     * @return {{{dataType}}}{{#isNullable}}|null{{/isNullable}}
     {{#deprecated}}
      * @deprecated
     {{/deprecated}}
@@ -378,7 +378,7 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}}{{/parentSchema}}{{^par
     /**
      * Sets {{name}}
      *
-     * @param {{{dataType}}}{{^required}}|null{{/required}} ${{name}}{{#description}} {{{.}}}{{/description}}{{^description}} {{{name}}}{{/description}}
+     * @param {{{dataType}}}{{#isNullable}}|null{{/isNullable}} ${{name}}{{#description}} {{{.}}}{{/description}}{{^description}} {{{name}}}{{/description}}
      *
      * @return self
     {{#deprecated}}