Tesseract parameters

Created by: LiteracyFanatic

This adds the parameter table for tesseract discussed in #233 (closed). The first three commits implement the editing, saving, and loading functionality and deal with any invalid rows in the table by silently dropping them before returning the parameters.

The fourth commit adds a validation layer that displays a message and focuses the first invalid cell. It works, but I'm not sure if there's a better way to organize the code for it.