Fix timeclock not using `timeclock-relative'

Replace some of timeclock's defuns with our own with the aim of fixing what is,
in my view, duplicate behaviour in the form of `timeclock-relative' and some
defuns accepting an optional parameter `today-only'.  This causes a particular
annoying problem when using some of timeclock's commands interactively where it
is not possible to pass t for `today-only' and the resulting output not being
what is desired.

The defuns remove the optional parameter `today-only' and use
`timeclock-relative' instead.