cubicweb-timesheet #1605421 Fix calendar icon image path [resolved]

The activities box displays an icon in its header. Currently, the icon path is hardcoded to data/office-calendar.png. Now that <base> tag is gone, this doesn't work any more, use data_url() instead.

prioritynormal
typebug
done in0.5.1
load0.000
load left0.000
closed by<not specified>