Add fortnight view to agenda
* doc/org.texi (Agenda commands): Document fortnight view.
* lisp/org-agenda.el (org-agenda-custom-commands-local-options):
(org-agenda-span): Add support for fortnight view.
(org-agenda-menu): Add fortnight view command.
(org-agenda-list):
(org-agenda-ndays-to-span): Add support for fortnight view.
(org-agenda-span-to-ndays): Add support for fortnight view.
(org-agenda-later): Add support for fortnight view.
(org-agenda-fortnight-view): New command.
(org-agenda-change-time-span): Add support for fortnight view.
(org-agenda-compute-starting-span): Add support for fortnight view.
This is a patch by Michael Gauland.