allow current directory for output and make it default

src/amdis/FileWriter.hpp

@@ -96,7 +96,7 @@ namespace AMDiS
     /// Implements \ref FileWriterInterface::writeFiles
     void writeFiles(AdaptInfo& adaptInfo, bool force) override
     {
-      test_exit(filesystem::exists(dir_), "Output directory '{}' does not exist!",dir_);
+      test_exit(dir_ == "." || filesystem::exists(dir_), "Output directory '{}' does not exist!",dir_);
 
       if (vtkSeqWriter_)
         vtkSeqWriter_->write(adaptInfo.time(), mode_);

src/amdis/FileWriterInterface.hpp

@@ -61,7 +61,7 @@ namespace AMDiS
 
   protected:
     std::string filename_ = "solution";
-    std::string dir_ = "output";
+    std::string dir_ = ".";
     std::string name_ = "solution";
   };