Add field category value in release notes for a single issue

pt-BR: Incluído valor do campo categoria para releases notes para tarefas.
Merge pull request #1 from levit/master

Add field category value in release notes for a single issue
add category replacement to de locale
add category replacement to en locale
add category replacement to ru locale
Merge pull request #107 from Silthus/master

Add Category to replaceable variables