This major update includes:
* a new key 'decade' for \gantttitlecalendar
* a new key 'time slot unit' for using one day, month or year per time
slot; this key replaces 'compress calendar' % a new macro \ganttvrule
for drawing arbitrary vertical rules (similar to the today rule), as
well as associated keys 'vrule', 'vrule offset', 'vrule label font',
and 'vrule label text' % a new key 'expand chart', which specifies that
a chart should expand horizontally to a given dimension % a new key
'title label text', which allows fine-tuning of title label formatting
% compatibility with the amsgen package
