prefer get_config_bool() where appropriate

for db input/output, we still use get_config_int() to convert to/from 0/1.
also for info() we prefer get_config_int() to show the real value.

src/context.rs

@@ -393,7 +393,7 @@ impl Context {
     }
 
     pub fn do_heuristics_moves(&self, folder: &str, msg_id: u32) {
-        if self.get_config_int(Config::MvboxMove) == 0 {
+        if !self.get_config_bool(Config::MvboxMove) {
             return;
         }