Add "template import" or "add --from-file" command

[igor-petruk]

"add" command has a limited application as is, because you likely need to do some debugging first before you make something a template.

Alternatively "template run" could work, as you could iterate on what you just run, but it is problematic, as not every save in "edit" mode is stored back to the original file. Maybe "edit" should do in-place editing