18: added c++ library

Closes #18

cpp/demo.cpp

@@ -17,10 +17,9 @@ int main(void) {
     form.entityuuid = account.uuid;
     auto entity = v.EntityGetEntity(account, form);
 
-     for (auto e = entity.begin(); e != entity.end(); ++e) {
-        std::cout <<  "activated:" << (*e).created << std::endl;
-        for (auto& kv : (*e).claims) {
-            std::cout << kv.first << "  "  << (*e).claims[kv.first].tags["registration"].value["value"] << std::endl;
+     for (auto &e : entity) {
+        for (auto& kv : e.claims) {
+            std::cout << kv.first << "  "  << e.claims[kv.first].tags["registration"].value["value"] << std::endl;
         }
     }
 }