JOC Cockpit should allow to log in when used without a JobScheduler Master

Current Situation

• The JOC Cockpit throws an error after login if used without a JobScheduler Master, i.e. if no Master has been installed.
• This behavior could be confusing for users who install the JOC Cockpit first and then install a JobScheduler Master.

Desired Behavior

• The JOC Cockpit should allow to login and should display the GUI when no JobScheduler Master is installed.
• This allows use of the JOC Cockpit with the YADE Command Line Client, see YADE-525. A JOC Cockpit Shiro configuration sample should be provided that limits permissions to use of the File Transfers view and History view.