[Usability]Name the font option

[Owen Taylor <otaylor redhat com>]

Adding another option to the font properties capplet,
need opinions on the name:

 Terminal font    
 Monospace font  - What Mozilla uses, (the CSS name)
 Monospaced font 
 Fixed width font - what KDE uses
 Typewriter font

The initial use is gnome-terminal, but it should effect
about anywhere that a monospace font is used.

I sort of like "Terminal" just because it is concrete
and refers to something definite.

Thanks,
                                        Owen