initial attempt at redcap calc fields/logic

[couthcommander]

questions

• when should "calc" fields be evaluated?
  • currently in .castRecords, which may be a bad choice
• where should they be evaluated?
  • currently in .castRecords, which may be a bad choice
• how should they be cast?
  • same as the non "_recalc" field
• how should results be summarized?
  • testing if [field] == [field]_recalc
• how should errors be handled?
  • result = NA
  • what's the error message?

todo

• map redcap functions to R (calculationEnvironment.R)
• handle evaluation of functions (redcapCalculations.R)
• casting
• summary table
• tests