[Minor] fix non-localized string in installer (install_stg_buildindex_*); fix wrong string_id in pophelp:url_schemes
// UK lang variables
tinyMCE.addToLang('layer',{
insertlayer_desc : 'Insert new layer',
forward_desc : 'Move forward',
backward_desc : 'Move backward',
absolute_desc : 'Toggle absolute positioning',
content : 'New layer...'
});