message: core: added assert for default case
  This should make a developer realize when an unsupported param type is
  being used.
diff: #include <string>
  #include <functional>
  #include <cstring> // for memcpy
  +#include <cassert>
  namespace dronecore {
  @@ -89,6 +90,7 @@ public:
  default:
  // This would be worrying
  LogErr() << "Error: unknown mavlink ext param type";
  + assert(false);
  break;
  }
  }
  