Removed classic GUI interface. Fixed typo with line number support.

- [config] Permanently removed classic GUI interface support. This
unintentionally created a problem where some users/GUI devs used this
compatibility mode and did not update to the new interface. So, there
were two interfaces in use, rather than just one like it was intended.
This removal should help everyone by forcing all GUIs to update and
updated GUI not having to support yet another interface.

- Fixed typo with line number support in jog mode.