Add some documentation templates

Not everything is correct at this point. The added
documentation comments will serve as a starting point
for apple docs.
Add better date formatter (LF-7415)

Format relative dates in a specific way: "" if in the future, "5s" if
under 1 minute, "5m" if under one hour, "5h" if under 24 hours, "6 Jul"
if under one year, "6 Jul 1990" if above one year.
submodule update