Improved handling of data type/dimension mismatches between nodes

Currently, two nodes cannot be joined together unless the input port on the downstream is configured to accept the type of data arriving from the upstream node. This makes sense in many cases, but sometimes there are straightforward conversions that could be done automatically. For example, it should generally be safe to convert an integer to a float, or a number to a 1-element array for array operations. In other cases the data are clearly incompatible, such as a dictionary entry and a numeric value.

For cases where datatype conversion is reasonable, changing the color of the input port would be a useful way to gently inform the user that the ports are mismatched without preventing the network from running — see for example ["coercion dots" in LabView](https://forums.ni.com/t5/LabVIEW-News/What-s-the-Deal-with-Coercion-Dots/ba-p/3480533?profile.language=en).