Add a presentation of Plume and of the instance on the homepage

Fixes #132

plume-models/src/users.rs

@@ -189,7 +189,9 @@ impl User {
                     long_description: String::new(),
                     short_description: String::new(),
                     default_license: String::new(),
-                    open_registrations: true
+                    open_registrations: true,
+                    short_description_html: String::new(),
+                    long_description_html: String::new()
                 })
             }
         };