add command line option to show full category name

This patch adds `clap` as a dependency for command-line argument
parsing, and introduces a `-f` flag to allow toggling whether or not the
full names of character classes are displayed.

utfdump_core/src/chardata.rs

@@ -231,7 +231,7 @@ impl Category {
 
 impl fmt::Display for Category {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}: {}", self.abbr(), self.full_name())
+        write!(f, "{}", self.abbr())
     }
 }