Migrate core source files to C++. Add yaml-cpp project as dependency (#2207)

By updating to this commit, Linux users have to regenerate Makefiles by re-running the configure script.

* Added yaml-cpp project as a 3rdparty library
* Migrated source files core to C++
* Updated configure scripts
* Make Linux installations compile *.cpp files
* Made server components' main source file C++
* Also made headers CPP-aware.

* Added basic C wrapper for yaml-cpp library
* YAML-node path is delimited by periods.
* Basic integer types and string are supported.
* Strings returned from this wrapper have to be freed with malloc.h::aFree
* Arrays (sequence) is supported with iterator wrapper.
* Remember to free every wrapper you create!

* Add yaml-cpp as dependency of common project
* Made the repo not ignore *.yml files

Thanks to @aleos89 and @Lemongrass3110.

3rdparty/yaml-cpp/src/directives.cpp

@@ -0,0 +1,22 @@
+#include "directives.h"
+
+namespace YAML {
+Directives::Directives() {
+  // version
+  version.isDefault = true;
+  version.major = 1;
+  version.minor = 2;
+}
+
+const std::string Directives::TranslateTagHandle(
+    const std::string& handle) const {
+  std::map<std::string, std::string>::const_iterator it = tags.find(handle);
+  if (it == tags.end()) {
+    if (handle == "!!")
+      return "tag:yaml.org,2002:";
+    return handle;
+  }
+
+  return it->second;
+}
+}