improved invoices with new renderer (#306)

* added docx renderer and demo template
* added csv renderer and demo template
* added xlsx renderer and demo template
* added ods renderer and demo template
* added user calculator
* added invoice documentation

tests/Twig/ExtensionsTest.php

@@ -124,6 +124,7 @@ class ExtensionsTest extends TestCase
     public function getMoneyData()
     {
         return [
+            ['0 €', null, 'EUR', 'de'],
             ['2.345 €', 2345, 'EUR', 'de'],
             ['2,345 €', 2345, 'EUR', 'en'],
             ['2,345.01 €', 2345.009, 'EUR', 'en'],

tests/Twig/MarkdownExtensionTest.php

@@ -41,6 +41,8 @@ class MarkdownExtensionTest extends TestCase
             "- test<br />\n- foo",
             $sut->timesheetContent("- test\n- foo")
         );
+        $this->assertEquals('', $sut->timesheetContent(null));
+        $this->assertEquals('', $sut->timesheetContent(''));
 
         $sut = new MarkdownExtension(new Markdown(), true);
         $this->assertEquals(