Simplify default configuration
    
    Make confdb load a base ldif like sysdb to initialize the db,
    makes it simpler to understand at first sight what is the default
    configuration.
    Make the parameter "command" optional. Derive the default command
    from available information.
    Make the debug level a global by default so that enabling debug for
    all components is as easy as passing just -d X to the sssd binary.