mod_admin/mod_admin_frontend: made admin more responsive. Added first version of frontend editor based on mod_admin.
(cherry picked from commit 5807a12b135b46616c8e6110d5227b7b0e35f7c3)

Conflicts:
	modules/mod_admin/templates/admin_edit.tpl
	modules/mod_seo_sitemap/templates/_admin_edit_content_seo_extra.tpl
	src/support/z_utils.erl