fix groupings label sort

Hi,

I want to fix sorting the chart grouping labels [1] and came up with two
solutions:

1.
extend [2] to look on all labels and not only on CF labels

2.
as far as I see there are only Date fields where the label sorting have
to be fixed so decide in [3] based on the SubFields if we sort 'raw' or
'numeric raw'


Is there something that speaks for or against one of the solutions?


Chris

[1] http://issues.bestpractical.com/Ticket/Display.html?id=29957
[2] https://github.com/bestpractical/rt/commit/83f0973
[3]
https://github.com/bestpractical/rt/blob/stable/lib/RT/Report/Tickets.pm#L148