C++: Moved all C++ examples to own folder

* moved C++ examples to a new cxx folder in
  examples
* added experimental C++ component
* added ESPException class to the C++ experimental
  component
* added test cases for ESPException and
  corresponding test macros

examples/cxx/experimental/experimental_cpp_component/include/esp_exception.hpp

@@ -0,0 +1,44 @@
+// Copyright 2019 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//         http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ESP_EXCEPTION_HPP_
+#define ESP_EXCEPTION_HPP_
+
+#ifdef __cpp_exceptions
+
+#include "esp_err.h"
+#include <exception>
+
+namespace idf {
+
+/**
+ * General exception class for exceptions on the ESP chips.
+ * All throwing code in IDF should use either this exception directly or a sub-classes.
+ */
+struct ESPException : public std::exception {
+    ESPException(esp_err_t error);
+
+    esp_err_t error;
+};
+
+/**
+ * Convenience macro to help converting IDF error codes into ESPException.
+ */
+#define CHECK_THROW(error_) if (error_ != ESP_OK) throw idf::ESPException(error_);
+
+} // namespace idf
+
+#endif // __cpp_exceptions
+
+#endif // ESP_EXCEPTION_HPP_