Adds Issue#status_was that returns the initial issue status.
Adds closed_on to issues API responses (#824).
Make sure that fields filled before tracker change are preserved.
Russian "label_last_n_weeks" translation changed by Mikhail Velkin (#12645)
Russian "label_x_issues" translation changed by Mikhail Velkin (#12645)
Bulgarian translation changed and updated by Ivan Cenov (#13190)
replace tabs to spaces at app/helpers/timelog_helper.rb
Fixed that updating the issue form was broken by r4011 when user is not allowed to add issues (#13188).
Adds field_closed_on to locales (#824).
Makes closed_on available as column and filter on the issue list (#824).
