bigfixing & new file: launcher/jsonutils.cpp

- launcher uses json parser from vcmi lib instead of one from Qt #1469
- fixed abilities overrides for some creatures #1476
- fixed hero portraits in seer huts #1402
- ttf fonts will render text in utf-8 mode. Not really useful at this point
- new settings entry, available in launcher: encoding. Unused for now.

lib/filesystem/Filesystem.cpp

@@ -300,7 +300,9 @@ std::vector<std::string> CResourceHandler::getAvailableMods()
 				continue;
 			}
 		}
-		foundMods.push_back(name);
+
+		if (!name.empty())
+			foundMods.push_back(name);
 	}
 	return foundMods;
 }