Make matches unique and smarter

Move the matching in the launcher to its own struct and make it so the
matches are unique and we don't end up with 2 or 3 matches for the same
program. Change the priorities so that they are bundled together with
the fuzzy matching score and thus very good keyword matches will beat
out very poor name matches.

src/desktop.rs

@@ -7,7 +7,7 @@ use std::fs;
 use std::io::Error as io_error;
 use std::io::ErrorKind;
 
-#[derive(Clone, Debug, Eq)]
+#[derive(Clone, Debug, Eq, Hash)]
 pub struct Desktop {
     pub entry_type: String,
     pub name: String,