Changed Name error to not include dashes

Several people have pointed out that, while Names can technically
include dashes, those dashes are turned into spaces when you save.  So
tweaked the descriptive message to stop saying that dashes are
appropriate.

querki/conf/messages

@@ -19,6 +19,6 @@ Thing.find.unknownName=No Thing found with that name
 
 Types.Name.empty=Names must have non-zero length
 Types.Name.tooLong=Names should not be excessively long
-Types.Name.badChars=Names may only contain letters, digits, dashes and spaces
+Types.Name.badChars=Names may only contain letters, digits, and spaces
 Types.Number.badFormat=Numbers should only contain digits
 Types.Text.tooShort={0} must be at least {1} characters long