doc: updated man pages for many tools

This patch perform simple fixes to the man pages and tool help page:
 - minor style updates, to get cleaner pages
 - option re-ordering, to have them in alphabetic order (easier to search for)
 - consistency updates for descriptions and number of dash
 - spell-checking

The biggest changes are:
 - wmagnify: the option 'vdisplay' was not documented at all;

 - getstyle: the list of attributes that are taken for the Style are now
described in their own section to clarify the page;

 - setstyle: the help page left thinking that the file argument was
optional, which is not the case;

 - wdread: as the Exit Code may be useful, and it is not unusable, it is
now documented;

 - wmgenmenu: added information about how the content of the menu is
generated;

 - wmsetbg: added a section about dithering/best-match because as nowadays
most screens are in True Color, the reason for the option may not be clear.

Signed-off-by: Christophe CURIS <christophe.curis@free.fr>

doc/wdwrite.1x

@@ -14,19 +14,19 @@ writes
 and
 .I value
 to the specified
-.I domain.
+.IR domain .
 .SH OPTIONS
 .TP
 .B \-\-help
-print a help message
+print a help message with the list of options
 .TP
 .B \-\-version
-print version number
+print the version of Window Maker from which the program comes
 .SH ENVIRONMENT
 .IP GNUSTEP_USER_ROOT
 specifies the initial path for the Defaults directory. "Defaults/" is
 appended to this variable to determine the actual location of the
-databases. If the varialbe is not set, it defaults to "~/GNUstep"
+databases. If the variable is not set, it defaults to "~/GNUstep"
 .SH FILES
 The domains reside in GNUSTEP_USER_ROOT/Defaults/
 .SH SEE ALSO