Reword a few of the reference documentation titles to better fit in with
the rest.
Do not use all-caps MODBUS for title.
Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>
Promote the Controller Area Network (CAN) subsystem reference
documentation from being part of the networking subsystem documentation
to having its own section.
The networking subsystem primarily deals with IP-based networking,
whereas CAN is a subsystem of its own.
Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>