Rename custom column php file. re #32

--HG--
rename : custom_column.php => customcolumn.php
Fix entry title. re #32
Change the default config for cops_x_accel_redirect to let PHP handle the
download. Should fix problem from KevNancy on IIS.

Warning all Nginx users who wants to still use X-Accel-Redirect must add
$config['cops_x_accel_redirect'] = "X-Accel-Redirect" in their config_local

fix #33
Add Custom columns through config. Only tested in HTML catalog for now

re #32
Release preparation