Trans: Add bg_BG language and fix monor strings

ChangeLog

dev/translation/autotranslator.class.php

dev/translation/autotranslator.php

htdocs/langs/ar_SA/errors.lang

htdocs/langs/bg_BG/admin.lang

htdocs/langs/bg_BG/agenda.lang

htdocs/langs/bg_BG/banks.lang

htdocs/langs/bg_BG/bills.lang

htdocs/langs/bg_BG/bookmarks.lang

htdocs/langs/bg_BG/boxes.lang

htdocs/langs/bg_BG/cashdesk.lang

htdocs/langs/bg_BG/categories.lang

htdocs/langs/bg_BG/commercial.lang

htdocs/langs/bg_BG/companies.lang

htdocs/langs/bg_BG/compta.lang

htdocs/langs/bg_BG/contracts.lang

htdocs/langs/bg_BG/deliveries.lang

htdocs/langs/bg_BG/dict.lang

htdocs/langs/bg_BG/donations.lang

htdocs/langs/bg_BG/ecm.lang