Improve transation files according to the new requrements

• In a standard ts file, the translation field will be filled in (in practice, the source content will often be copied there) and the unfinished tag will not be found. And also there will be no language tag in this file (there will be no language="en" so such a translation works by default for all languages where there is no explicit translation)
• The Russian translation file will contain the label language="ru", as expected. In the lines where you need to save a term in English, you need to explicitly duplicate the same term in English in the translation line (do not use an empty line with the unfinished tag)

Therefore, unfinished status is not expected in translation files. Their absence can be used to judge the readiness of the entire translation.

NB. Other projects in the internets may have a different approach to the translation. There could be an engineering template in English that is not translated (contains only empty translation fields marked unfinished). And for English (British or American) separate files are prepared.