Merge branch 'backport-time-tracking-ce' into 'master'

app/assets/javascripts/diff_notes/diff_notes_bundle.js.es6

app/assets/javascripts/issuable/issuable_bundle.js.es6

.../issuable/time_tracking/components/collapsed_state.js.es6

.../issuable/time_tracking/components/comparison_pane.js.es6

...suable/time_tracking/components/estimate_only_pane.js.es6

...ripts/issuable/time_tracking/components/help_state.js.es6

...issuable/time_tracking/components/no_tracking_pane.js.es6

.../issuable/time_tracking/components/spent_only_pane.js.es6

...pts/issuable/time_tracking/components/time_tracker.js.es6

...cripts/issuable/time_tracking/time_tracking_bundle.js.es6

app/assets/javascripts/lib/utils/pretty_time.js.es6

app/assets/javascripts/lib/vue_resource.js.es6

app/assets/javascripts/subbable_resource.js.es6

app/assets/stylesheets/framework/variables.scss

app/assets/stylesheets/pages/issuable.scss

app/helpers/issuables_helper.rb

app/models/concerns/issuable.rb

app/models/concerns/time_trackable.rb

app/models/timelog.rb

app/serializers/issuable_entity.rb