Add support to control hostname and control port

[letzya]

Tyk demo should use best practices where possible, for example, control port and hostname.
Currently, if you set up the two env vars, it will not work.
We need to add a hostname to the host update script and open the port in the docker compose. Also we'd need to update the postman env and collection.

TYK_GW_CONTROLAPIPORT=9080
TYK_GW_CONTROLAPIHOSTNAME=tyk-gateway-control