Add a gear_lever_position signal to official set.
Add a gear_lever_position signal to official set.

This signal is primarily used on vehicles with continuously variable
transmissions, where the transmission_gear_position signal is not
useful.

openxc/openxc-message-format,mgiannikouris/openxc-message-format,mgiannikouris/openxc-message-format,openxc/openxc-message-format,openxc/openxc-message-format,mgiannikouris/openxc-message-format,mgiannikouris/openxc-message-format