Spike on /set-cookie

[#80222490]
Unescape post form values it CT set-cookie endpoint
Add CORS headrs to set-cookie response
Set allow-origin to jsdemo for testing
Send correct headers for CORS on TC /set-cookie endpoint

[#80222490]
Merge branch 'set-cookie-endpoint' into develop

[#80222490]

Conflicts:
	src/trafficcontroller/dopplerproxy/doppler_proxy.go
	src/trafficcontroller/dopplerproxy/doppler_proxy_test.go