core: added 'no_touch' option with a new m_edge:delete/5.
core: added #media_update_done{} notification.
mod_base: small fixes for async validations. Added optional validations on the form itself, to be run after all other validations pass.
mod_l10n: added 'is_only_known' option, to suppress adding a selected value as an extra option if it is unknown in the list of countries.
This is useful to prevent submit of unknown (or unwanted) country codes.