Expand references in calculus function arguments

[puremourning]

This allows for the use of variables as arguments to functions.

In particular, the following is now possible:

 "configuration": {
   "request": "attach",
   "processId": "${PickProcess(\"${programName}\")}",
   "program": "$BUILD/platform/bin64/${programName}",
   "expresssions": "native"
 }

The result is that you're asked for the program name and it filters for that, and uses it as the binary.

Doesn't work for function-calls-inside-function-calls because of not enough escaping levels for parameters, but that's probably OK. The above is a real use case however, and it works.

This is mad, gnarly stuff which probably shouldn't be used, but that's also true of the whole of this entire macro-templating system, which honestly needs to be compeltely ditched!

[puremourning]

This change is