[js] make _loadAjaxHtmlHead aware of mod_concat-like urls
_loadAjaxHtmlHead keeps track of already imported resources (js / css)
to make sure they're not included twice, but with mod_concat-like urls,
things get a bit more complicated :
if BASE_URL/data??foo.js,bar.js is already imported, then loading :
BASE_URL/data??bar.js,spam.js should only load spam.js
###############################################################################
#
# Put here information about external resources / styles used by your cube,
# or to overides existing UI properties.
#
# Existing properties are available through the `sheet` dictionary available
# in the global namespace. You also have access to a `data` function which
# will return proper url for resources in the 'data' directory.
#
# /!\ this file should not be imported /!\
###############################################################################
# CSS stylesheets to include in HTML headers
# uncomment the line below to use template specific stylesheet
# STYLESHEETS = sheet['STYLESHEETS'] + [data('cubes.%(cubename)s.css')]