Display current stopwatch in navbar (#14122)

* add notification about running stopwatch to header

* serialize seconds, duration in stopwatches api

* ajax update stopwatch

i should get my testenv working locally...

* new variant: hover dialog

* noscript compatibility

* js: live-update stopwatch time

* js live update robustness

options/locale/locale_en-US.ini

@@ -15,6 +15,7 @@ page = Page
 template = Template
 language = Language
 notifications = Notifications
+active_stopwatch = Active Time Tracker
 create_new = Create…
 user_profile_and_more = Profile and Settings…
 signed_in_as = Signed in as
@@ -1139,13 +1140,15 @@ issues.lock.title = Lock conversation on this issue.
 issues.unlock.title = Unlock conversation on this issue.
 issues.comment_on_locked = You cannot comment on a locked issue.
 issues.tracker = Time Tracker
-issues.start_tracking_short = Start
+issues.start_tracking_short = Start Timer
 issues.start_tracking = Start Time Tracking
 issues.start_tracking_history = `started working %s`
 issues.tracker_auto_close = Timer will be stopped automatically when this issue gets closed
 issues.tracking_already_started = `You have already started time tracking on <a href="%s">another issue</a>!`
-issues.stop_tracking = Stop
+issues.stop_tracking = Stop Timer
 issues.stop_tracking_history = `stopped working %s`
+issues.cancel_tracking = Discard
+issues.cancel_tracking_history = `cancelled time tracking %s`
 issues.add_time = Manually Add Time
 issues.add_time_short = Add Time
 issues.add_time_cancel = Cancel
@@ -1154,8 +1157,6 @@ issues.del_time_history= `deleted spent time %s`
 issues.add_time_hours = Hours
 issues.add_time_minutes = Minutes
 issues.add_time_sum_to_small = No time was entered.
-issues.cancel_tracking = Cancel
-issues.cancel_tracking_history = `cancelled time tracking %s`
 issues.time_spent_total = Total Time Spent
 issues.time_spent_from_all_authors = `Total Time Spent: %s`
 issues.due_date = Due Date