support cluster connection management

[amyXia1994]

users need to have easy access to clusters, including:

• can easily create a connection to a cluster with authentication(using credentials or login)
  • see a user-friendly message when the connection succeeded
  • see a user-friendly error message when the connection failed
• can check the cluster connection status( for example, through obvious mark on the cluster information)
• can re-connect to the previous connected clusters without inputting credentials or login repeatedly(unless the login status expired)
• can modify or remove existing cluster connection info