[NTG-context] Fine-tuning of aps style

To cite like [1, p. 101] \cite[righttext={\nbsp p.~101}][Hankins:2014] works, but has no comma \cite[righttext={, p.~101}][Hankins:2014] produces no page \cite[righttext={,\nbsp p.~101}][Hankins:2014] gives no page at all \cite[righttext={\nbsp, p.~101}][Hankins:2014] gives no page at all. righttext seems to be reluctant over the initial comma right after the reference number.