Fix negative timestamps format

[will-moore]

Noticed bug with negative timestamps using hh:mm:ss format or mm:ss format since we round the hrs and minutes down in the UI and export script.

To test, check that the timestamps are shown correctly on this figure (screenshot shows current bug) e.g. 0:00:-1 and -1:59:59

[jburel]

Something is out of synch in the display

[jburel]

Check the time values one is -00:00:value one is 00:00:-value

[will-moore]

@jburel Sorry - didn't list this for standup today but 00:00:-value is fixed in right panel.
One issue I noticed: If you have a negative time (e.g 100 milliseconds) and you show hh:mm:ss`` or ``hh:mm``, they will currently appear as -00:00:00```, which is technically correct (they are negative) but does that look too wrong?

[jburel]

Right-hand panel now

[jburel]

Having the "negative" zeros do not look good as you say, in that case it should ``00:00``

[jburel]

This looks better

[jburel]

Outside the scope of this PR but for long lasting timelapse [hrs] and [hrs:mins] will be useful

[jburel]

[jburel]

RFE #384