Support echo input in normal execution

[ywangd]

Currently, the run builtin command echos its input command, e.g. run 'file.es' echos every input command. But peek file.es does not.

It could be useful to support input echoing for peek file.es for presentation purpose. Another issue with input echoing is that the input echoing is not literal. For example, GET / will be echoed as GET / {}, where the {} means there is no option given to the API call. This is non-ideal because neither peek nor kibana console uses this syntax.