Added prompt escape code expansion flag to echo, -p

Added non-formatted runtime to prompt escape codes

Added prompt escape code that expands to the output of a shell function

Reworked internal logic for termios control

src/state.rs

@@ -686,7 +686,6 @@ impl MetaTab {
   pub fn stop_timer(&mut self) -> Option<Duration> {
     self
       .runtime_start
-      .take() // runtime_start returns to None
       .map(|start| start.elapsed()) // return the duration, if any
   }
 }