More format() changes

[Rik]

All,

Per suggestions, I changed the behavior of format when called with no
arguments to also include setting the uppercase_format variable to the
default (https://hg.savannah.gnu.org/hgweb/octave/rev/2545345f8bd9). 
Subsequently, I changed format to accept multiple arguments
(https://hg.savannah.gnu.org/hgweb/octave/rev/1ef42010c53b).  It is now
possible to set everything in one line.  For example, "format long e
compact uppercase".

--Rik