Expanded the functionality of the parameters helper - you can now spe…

…cify

default values for which the types can be automatically inferred if
needed. This means the "values" vector size can be smaller than the
parameter pack.

Example:
```
const auto [a,b,c,d] = emergent::parameters::get(values, 5, "hi"s, 3.14, true );
```

include/emergent/Clap.hpp

@@ -40,8 +40,25 @@ namespace emergent
 
 			return create_tuple<Types...>(std::index_sequence_for<Types...> {}, values);
 		}
+
+
+		template <typename T> T retrieve(const std::vector<std::string> &values, const size_t index, const T &def)
+		{
+			return index < values.size() ? transform<T>(values[index]) : def;
+		}
+
+		template <typename... Types, std::size_t... Is> auto create_tuple(std::index_sequence<Is...>, const std::vector<std::string> &values, Types... defaults)
+		{
+			return std::make_tuple(retrieve<Types>(values, Is, defaults)...);
+		}
+
+		template <typename... Types> std::tuple<Types...> get(const std::vector<string> &values, Types... defaults)
+		{
+			return create_tuple<Types...>(std::index_sequence_for<Types...> {}, values, defaults...);
+		}
 	}
 
+
 	// A command-line argument parser.
 	class Clap
 	{