gitweb: Separate filling list of projects info

gitweb: Separate filling list of projects info

Extract filling project list info, i.e. adding age, description, owner
and forks information, into fill_project_list_info() subroutine.  This
is preparation for smart pagination and smart searching (to make it
possible to calculate/generate info only for those projects which will
be shown).

Small changes compared to original version to improve readability
(comments, names of variables, named loops).

Additionally, store both full ('descr_long') and shortened ('descr')
project description in Perl's internal form (using to_utf8).

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>