Add support for named function parameters

[amitchone]

No description provided.

[garethpotter]

A minor quibble is that ...NamedUserFunction is not really the right name for this (the functions already have names), but I am not quite sure what would be both correct and concise.

[amitchone]

A minor quibble is that ...NamedUserFunction is not really the right name for this (the functions already have names), but I am not quite sure what would be both correct and concis

Absolutely agree, ...NamedParametersUserFunction was too verbose IMO and I struggled for something better... That said, I've only got a handful of call sites so it's not the end of the world...