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/emit.cpp

@@ -0,0 +1,25 @@
+#include "yaml-cpp/node/emit.h"
+#include "yaml-cpp/emitfromevents.h"
+#include "yaml-cpp/emitter.h"
+#include "nodeevents.h"
+
+namespace YAML {
+Emitter& operator<<(Emitter& out, const Node& node) {
+  EmitFromEvents emitFromEvents(out);
+  NodeEvents events(node);
+  events.Emit(emitFromEvents);
+  return out;
+}
+
+std::ostream& operator<<(std::ostream& out, const Node& node) {
+  Emitter emitter(out);
+  emitter << node;
+  return out;
+}
+
+std::string Dump(const Node& node) {
+  Emitter emitter;
+  emitter << node;
+  return emitter.c_str();
+}
+}  // namespace YAML