New: Add greek language

htdocs/langs/el_GR/admin.lang

htdocs/langs/el_GR/agenda.lang

htdocs/langs/el_GR/banks.lang

htdocs/langs/el_GR/bills.lang

htdocs/langs/el_GR/boxes.lang

htdocs/langs/el_GR/cashdesk.lang

htdocs/langs/el_GR/categories.lang

htdocs/langs/el_GR/commercial.lang

htdocs/langs/el_GR/companies.lang

htdocs/langs/el_GR/compta.lang

htdocs/langs/el_GR/contracts.lang

htdocs/langs/el_GR/deliveries.lang

htdocs/langs/el_GR/dict.lang

htdocs/langs/el_GR/domains.lang

htdocs/langs/el_GR/donations.lang

htdocs/langs/el_GR/ecm.lang

htdocs/langs/el_GR/errors.lang

htdocs/langs/el_GR/exports.lang

htdocs/langs/el_GR/ftp.lang

htdocs/langs/el_GR/help.lang