Improved Phobos dox

[Andrei Alexandrescu]

I finally gathered strength to rebase 
https://github.com/D-Programming-Language/dlang.org/pull/271 manually, 
which was every bit as involved as I feared.

I hope I didn't mess up anything, reviews appreciated.

That diff includes a new page navigation scheme. (Wasn't the main 
purpose of the diff but found it a nice perk.) I see it as a 
transitional stage toward the larger transition to one-page-per-entity 
that Sönke has proposed.

Check out the new navigation at 
http://erdani.com/d/phobos/std_array.html. The ugly "Jump to" list as 
the top gets replaced by a slick drop-down. Once you jump to a name, you 
can go back by pressing the up arrow on the right or simply go to top.


Andrei