reactive: add PropSignal. To see what it looks like. Not sure if we keep it.
reactive: add PropSignal. To see what it looks like. Not sure if we keep it.

sesh/flexx,thezawad/flexx,lovesnow/flexx,almarklein/flexx,JohnLunzer/flexx,JohnLunzer/flexx,hungle90/flexx,manashmndl/flexx,manashmndl/flexx,stonebig/flexx,abhishekgahlot/flexx,JohnLunzer/flexx,dut3062796s/flexx,shaunstanislaus/flexx,kevinlondon/flexx,a9261/flexx,sesh/flexx,alihalabyah/flexx,NateChambers/flexx,kuyun-zhangyang/flexx,kevinlondon/flexx,lancheng/flexx,amanikamail/flexx,almarklein/flexx,zoofIO/flexx,Muktesh01/flexx,chengjunjian/flexx,hungle90/flexx,amanikamail/flexx,a9261/flexx,synmnstr/flexx,dut3062796s/flexx,thezawad/flexx,almarklein/flexx,synmnstr/flexx,lancheng/flexx,gale320/flexx,Muktesh01/flexx,stonebig/flexx,zoofIO/flexx,jrversteegh/flexx,abhishekgahlot/flexx,kuyun-zhangyang/flexx,chengjunjian/flexx,lovesnow/flexx,NateChambers/flexx,alihalabyah/flexx,jrversteegh/flexx,gale320/flexx,shaunstanislaus/flexx