[Orgmode] org-clock mode-line format configuration

[Kiwon Um]

Dear orgmode dev team:

When the clock is started on an item, the item is shown on the mode
line. But the string on the mode line just shows the raw string of the
item, so sometimes it looks ugly when it contains a link.

So I suggest to make it customizable, or to vanish the link string, e.g.
using
 (replace-regexp-in-string "\\[\\[.*\\]\\[\\(.*\\)\\]\\]" "\\1" str)

Sincerely,

Kiwon Um