Add edit features: Find, Delete-Line

Adds incremental Find command (CTRL-F), and CTRL-Del to delete a line.

While I think most of us cheat and edit externally, it's useful when making small changes to be able to use the built-in edit command. But without Find, just getting to the point to make the small change is slow. Still needs Copy & Paste of course, but this change adds Highlight as a concept too which might help a little.
Indent using spaces, please.