general keybindings (#775)

* general keybindings

* get value function

* check error for keybinding

* cmd and send for keybingins

* better error message

crates/nu-command/src/conversions/into/string.rs

@@ -220,7 +220,7 @@ pub fn action(
         },
 
         Value::Filesize { val: _, .. } => Value::String {
-            val: input.clone().into_string(", ", config),
+            val: input.into_string(", ", config),
             span,
         },
         Value::Nothing { .. } => Value::String {

crates/nu-command/src/formats/to/md.rs

@@ -207,7 +207,7 @@ pub fn group_by(values: PipelineData, head: Span, config: &Config) -> (PipelineD
                 .or_insert_with(|| vec![val.clone()]);
         } else {
             lists
-                .entry(val.clone().into_string(",", config))
+                .entry(val.into_string(",", config))
                 .and_modify(|v: &mut Vec<Value>| v.push(val.clone()))
                 .or_insert_with(|| vec![val.clone()]);
         }