calcurse-caldav: add custom data directory support
calcurse-caldav: add custom data directory support

Added the --datadir flag to calcurse-caldav which enables to specify a
custom calcurse data directory similarly to the -D flag in calcurse.

Signed-off-by: Lukas Fleischer <c9ca73f8336dcfb037ec2c2abf52d80a6847a5cd@calcurse.org>

lfos/calcurse,lfos/calcurse,lfos/calcurse