Add support for ?then built-in in Responsys

Brandon McConnell - PRB

The Free Marker Java templating language that Responsys RPL is based/built on supports a built-in for ?then which works similarly to a ternary expression (shorthand if/else).

The ?string built-in works this way already as well, except that the ?string built-in always evaluates to a string, whereas ?then can return any data-type. For example:

// already supported
someCondition?string("whenTrue", "whenFalse") // works fine
someCondition?string(1, 2) // throws an error, requires ?then

// not yet supported
someCondition?then(1, 2) // works fine in Free Marker

I propose adding native support for ?then within Oracle Responsys RPL.