fix missed translation

translate the modification from 'never' to 'rarely'.
translated JavaGuide5.md
Merge branch '2.1' of github.com:garbagetown/playdocja into 2.1
copy the translations in common with 2.0.4. refs #253
translation the part that has been modified from 2.0.4. refs #253
copy the translations in common with 2.0.4. refs #255
update issue tracker information following original. refs #255
add translated tag. refs #255