Converting translation files

From GNU Gettext Qt Linguist

1. Convert knotter_knotter-(lang).po into knotter_(lang).ts (lconvert)
2. Add knotter_(lang).ts to translations.pri
3. Update the translations (lupdate)
4. Compile knotter_(lang).ts into knotter_(lang).qm (lrelease)

Example:

lconvert -i data/translations/knotter_knotter-ru.po -o data/translations/knotter_ru.ts
lconvert -i data/translations/knotter_knotter-en_GB.po -o data/translations/knotter_en_GB.ts
lupdate knotter.pro
lrelease knotter.pro