Merge changes in master to beta branch (concurrency fixes)

src/main.rs

@@ -84,6 +84,11 @@ fn check_db() {
             exit(1);
         }
     }
+
+    // Turn on WAL in SQLite
+    use diesel::RunQueryDsl;
+    let connection = db::get_connection().expect("Can't conect to DB");
+    diesel::sql_query("PRAGMA journal_mode=wal").execute(&connection).expect("Failed to turn on WAL");
 }
 
 fn check_rsa_keys() {