Polymorphic Record class, more stderr options

Added string repr to list of accepted property values.
(Estimation.method can be assigned 1 or '1' as well as 'qrpem')
none/central-diff/forward-diff method options combined into stderr
Script to print NLME7.exe arguments from last run

Makes some of assumptions, but it is useful in quickly printing out what
command-line arguments were used for the last GUI run.