TS-4060: add JSON support consistently for traffic_layout
TS-4060: add JSON support consistently for traffic_layout

This closes #417.

PSUdaemon/trafficserver,clearswift/trafficserver,persiaAziz/trafficserver,clearswift/trafficserver,PSUdaemon/trafficserver,SolidWallOfCode/trafficserver,rahmalik/trafficserver,reveller/trafficserver,PSUdaemon/trafficserver,rpufky/trafficserver,bryancall/trafficserver,reveller/trafficserver,reveller/trafficserver,rahmalik/trafficserver,persiaAziz/trafficserver,vmamidi/trafficserver,chenglongwei/trafficserver,duke8253/trafficserver,chenglongwei/trafficserver,rahmalik/trafficserver,chitianhao/trafficserver,duke8253/trafficserver,davidbz/trafficserver,rpufky/trafficserver,persiaAziz/trafficserver,rpufky/trafficserver,clearswift/trafficserver,dyrock/trafficserver,rpufky/trafficserver,duke8253/trafficserver,clearswift/trafficserver,chitianhao/trafficserver,pbchou/trafficserver,rahmalik/trafficserver,PSUdaemon/trafficserver,davidbz/trafficserver,reveller/trafficserver,taoyunxing/trafficserver,davidbz/trafficserver,dyrock/trafficserver,taoyunxing/trafficserver,dyrock/trafficserver,persiaAziz/trafficserver,SolidWallOfCode/trafficserver,davidbz/trafficserver,bryancall/trafficserver,duke8253/trafficserver,SolidWallOfCode/trafficserver,clearswift/trafficserver,vmamidi/trafficserver,chenglongwei/trafficserver,vmamidi/trafficserver,taoyunxing/trafficserver,pbchou/trafficserver,pbchou/trafficserver,SolidWallOfCode/trafficserver,clearswift/trafficserver,reveller/trafficserver,vmamidi/trafficserver,chenglongwei/trafficserver,chitianhao/trafficserver,taoyunxing/trafficserver,chenglongwei/trafficserver,bryancall/trafficserver,taoyunxing/trafficserver,SolidWallOfCode/trafficserver,persiaAziz/trafficserver,vmamidi/trafficserver,davidbz/trafficserver,PSUdaemon/trafficserver,rpufky/trafficserver,rpufky/trafficserver,persiaAziz/trafficserver,rahmalik/trafficserver,PSUdaemon/trafficserver,chitianhao/trafficserver,rpufky/trafficserver,davidbz/trafficserver,dyrock/trafficserver,rahmalik/trafficserver,clearswift/trafficserver,taoyunxing/trafficserver,reveller/trafficserver,SolidWallOfCode/trafficserver,chitianhao/trafficserver,reveller/trafficserver,SolidWallOfCode/trafficserver,duke8253/trafficserver,bryancall/trafficserver,chenglongwei/trafficserver,chitianhao/trafficserver,taoyunxing/trafficserver,dyrock/trafficserver,rahmalik/trafficserver,taoyunxing/trafficserver,vmamidi/trafficserver,persiaAziz/trafficserver,PSUdaemon/trafficserver,chenglongwei/trafficserver,chenglongwei/trafficserver,clearswift/trafficserver,rpufky/trafficserver,taoyunxing/trafficserver,clearswift/trafficserver,dyrock/trafficserver,rahmalik/trafficserver,rahmalik/trafficserver,duke8253/trafficserver,reveller/trafficserver,duke8253/trafficserver,bryancall/trafficserver,reveller/trafficserver,chitianhao/trafficserver,pbchou/trafficserver,persiaAziz/trafficserver,pbchou/trafficserver,PSUdaemon/trafficserver,rpufky/trafficserver,pbchou/trafficserver,PSUdaemon/trafficserver,bryancall/trafficserver,dyrock/trafficserver