[O] Agenda optimization (new worg page and new defaults)

[Bastien]

Hi all,

I wrote a worg page with some advice on how to speed up agenda
commands:

  http://orgmode.org/worg/agenda-optimization.html

I also reverted the change for two variables:

  org-agenda-inhibit-startup
  org-agenda-dim-blocked-tasks

Those used to be respectively nil and t, and while working on
agenda speedup, I changed them to t and nil.  But the reasoning
behind this was weak.  Users who need to speed up their agenda
commands are most probably long-time users and they will be able
to stumble on the variables and/or on the worg page.

New users expect the agenda to keep agenda files folded when
running an agenda command, and to dim blocked tasks by default.

So -- this is now the case:

  http://orgmode.org/cgit.cgi/org-mode.git/commit/?id=c00a43

(Note that it's by the same reasoning that
`org-agenda-use-tag-inheritance' is set to (todo search timeline
agenda) instead of nil, which would speed up most agendas.)

Sorry for the instability here in master.

I also set `org-time-clocksum-use-effort-durations' to nil by
default, because it would surprise many users if they suddenly
see new values in their clocktables.

Thanks to Tassilo Horn and John Wiegley who let me rethink
about all these defaults!

-- 
 Bastien