make blog/instance description a SafeString

long_description & short_description's documentation say they can be
Markdown, but they are String, not SafeString.

This led to escaped strings being printed in the editor
https://github.com/Plume-org/Plume/issues/220

src/routes/instance.rs

@@ -125,8 +125,8 @@ fn update_settings(conn: DbConn, admin: Admin, form: LenientForm<InstanceSetting
             instance.update(&*conn,
                 form.name.clone(),
                 form.open_registrations,
-                form.short_description.clone(),
-                form.long_description.clone());
+                form.short_description.clone().to_string(),
+                form.long_description.clone().to_string());
             Redirect::to(uri!(admin))
         })
         .map_err(|e| Template::render("instance/admin", json!({

src/setup.rs

@@ -6,6 +6,7 @@ use std::io;
 use std::path::Path;
 use std::process::{exit, Command};
 use rpassword;
+use plume_models::safe_string::SafeString;
 
 use plume_models::{
     DB_URL,
@@ -152,8 +153,8 @@ fn quick_setup(conn: DbConn) {
         public_domain: domain,
         name: name,
         local: true,
-        long_description: String::new(),
-        short_description: String::new(),
+        long_description: SafeString::new(&<String>::new()),
+        short_description: SafeString::new(&<String>::new()),
         default_license: String::from("CC-0"),
         open_registrations: true,
         short_description_html: String::new(),