Updates to the command-line shell. Simplify the banner message. Add the

Updates to the command-line shell.  Simplify the banner message.  Add the
".save" command as an alias for ".backup".  When starting with no arguments,
include a banner message warning that the database is transient and in-memory
and mention the ".open" command.

FossilOrigin-Name: f5ad1e1bf2828c5da70c1ff944d8212036142e6f