Add Ingress TLS support (#1326)

This PR aims to add the Ingress TLS support by specifying the
TLS secret when creating/updating the HTTP trigger.

Command example:

fission route create --name foo \
    --url /foo/{bar} --function foofn --createingress \
    --ingressannotation "nginx.ingress.kubernetes.io/ssl-redirect=false" \
    --ingressannotation "nginx.ingress.kubernetes.io/use-regex=true" \
    --ingressrule "*=/foo/*"
    --ingresstls "foobartls"

pkg/apis/fission.io/v1/types.go

@@ -582,6 +582,11 @@ type (
 		// host is empty or "*", the rule applies to all
 		// inbound HTTP traffic.
 		Host string `json:"host"`
+
+		// TLS is for user to specify a Secret that contains
+		// TLS key and certificate. The domain name in the
+		// key and crt must match the value of Host field.
+		TLS string `json:"tls"`
 	}
 
 	// KubernetesWatchTriggerSpec