Multiple connections in input node

[Daguerreo]

I've merged ExMix's paceholder#213 which allow ConnectionPolicy::Many for input ports.

In this way one or more input ports can have an arbitrary number of input. It appears to be more reliable of a dynamic addition of port as showed in paceholder#209 and paceholder#212.

I modified the calculator example to make it more consistent with the coding rule and some minor fix. In addition I modified the caption to show exactly how many connections are sending data to the node, since a single connection to a multi input node can be attached several time and the thing cannot be seen due to the connection overlapping.