hide cas ticket from web portal

In the previous implementation, when login the url will shown as:
http://localhost:8000/?ticket=ST-5WzYs6SD2A#/
this patch aims to hide the ticket mechanism.

1) add /api/v1/auth/signin_return to process login verify
2) refactor code, leverage SignBaseHanlder() to manage casclient

Change-Id: I62e23eb69ee52304c30753e861b4f0a4e0d45541
Signed-off-by: SerenaFeng <feng.xiaowei@zte.com.cn>