Set GUI options like size and fonts *after* the configuration
file is read to allow the file to override the defaults.
Changed 'Last Command' semantics to include items selected
from Command History, but only if they were manually modified.
Changed logic of MAXNESTING to operate correctly when this
variable is set to 0 - this inhibits all user-define variable substitution.
Added MAXHIST variable and supporting logic to bound the size of
the Command History.
Began adding the infrastructure to support setting options in the
configuration file.  MAXHIST, MAXNESTING, HEIGHT, WIDTH now
can be set this way.
Began implementing MAXDIR to bound size of Directory Menu
contents.
Changed semantics of how options are read at startup.
The Configuration File (if any) is read before any other
environment or command line options are processed.  This
allows the configuration file to override program defaults
via options specified by the user in that file.