Local countdown

[p0358]

• Add local countdown if departure is close enough (so we get a smooth second-by-second cooldown before the next refresh)
• Fix ttss_base if project is not installed in web root (a dot for relative path)
• Fix in map.js for green border if tram is already on stop/loop (as it was done in previous pull request in index.js, didn't notice the one in map.js)

Please review.

[jacekkow]

I would like to see such changes:

• do not call loadTimes inside setInterval function - this may cause weird behavior if many trains should arrive in succession (eg. in 2, 4 and 6 seconds - it may result in three calls each canceling the preceding one),
• IMHO the way to go should be to keep references to <tr> and relevant <td> elements along with actualRelativeTime (maybe use td.dataset),
• go through all the elements every second and only update text content (plus className), optionally on-demand (ie. compare what is generated with current value and setText if required - but I am not sure how much of a performance hit will incur from not doing it, if any). This would also make should_activate_smooth_timer obsolete.

This would lower both number of modifications and additional code required - pretty much only function for setting status text and proper className should be extracted and used).

As you have stated - updating half of the DOM tree every second is no good.

It would also be unnecessary DOM updating every second without any visual change.

Thanks for the contribution!