Template-specific text holes

[creachadair]

We've talked before about having a nice UI for dynamically picking text locations. A simpler approach (and easier to implement) would be to allow a template to designate its own regions of interest. The UI for creating macros can still be simple (just some text fields) and a go button, but instead of fixed top/bottom locations we could have those fields point to specific targets.

1. Add data to the template record to record locations where text should go.
2. When creating a macro, populate the text fields based on the template's locations.
3. Include those locations in the text lines when creating the macro.