deactivating quickcheck narrowing examples to find out if this causes the system error on the current isatest

support for detached Bash_Job with some control operations;

allow catalog entries to be commented-out;

support external processes with explicit environment;

include COMPONENT/etc/sessions as catalog for more directories, for improved scalability with hundreds of entries (notably AFP);
misc tuning and simplification;

less redundant data structures;

clarified topological ordering: preserve order of adjacency via reverse fold;

support Session.Queue with ordering and dependencies;

clarified signature;

more explicit treatment of initial Pure sessions;