afb-monitor: Add session and rework permissions

afb-monitor: Add session and rework permissions

The new verb session is available to get session info and
to renew the token. See examples below.

The permission required is now just to being check
meaning having the token.

Example:

afb-client-demo -H localhost:5555/api?token=456
monitor session
ON-REPLY 1:monitor/session: OK
{
  "response":{
    "uuid":"5a30c118-319c-43a2-82d5-fc2198d01938",
    "token":"",
    "timeout":32000000,
    "remain":31999985
  },
  "jtype":"afb-reply",
  "request":{
    "status":"success",
    "uuid":"5a30c118-319c-43a2-82d5-fc2198d01938"
  }
}
monitor session {"refresh-token":true}
ON-REPLY 5:monitor/session: OK
{
  "response":{
    "uuid":"5a30c118-319c-43a2-82d5-fc2198d01938",
    "token":"2f60faf8-ad04-457e-9f56-5c0c20b5f1fc",
    "timeout":32000000,
    "remain":32000000
  },
  "jtype":"afb-reply",
  "request":{
    "status":"success",
    "token":"2f60faf8-ad04-457e-9f56-5c0c20b5f1fc"
  }
}

Change-Id: Ic93bae80616e5dad1640e73ac9f472b7b385104f
Signed-off-by: José Bollo <jose.bollo@iot.bzh>