Possibility to specify a .calendar in an .ancestry

[Liantefaron]

Use case / Benefit: Make the birthdates use the in-game .calendar of a certain in-game race/culture/region, configured via the relevant .ancestry file.

Idea: Add something like

"birthdates_calendar": "Some Calendar Name",

under common_options within an .ancestry file.

Edit: The Calendar specified in General Settings should be used for out-of-game dates (i.e. RtPG sessions), the Calendar associated with a character should relate to the in-game birthday and the in-game date in session logs.