Adrien Di Mascio <Adrien.DiMascio@logilab.fr> [Mon, 28 Mar 2011 15:23:57 +0200] rev 7117
[facets] closes #1569459 (date-range facet with year < 1900)
use lgc.date.ustrftime() and lgc.date.ticks2datetime to convert js date ticks and
have a chance to handle dates with year < 1900.