Calendar

Signed-off-by: o_koeh01 <o_koeh01@uni-muenster.de>
HUP small changes: - Moved template categories, template categories by folder structure instead of filename prefix, - removed occurence of $CFG in lang files, - added standard nav icons for template(categories) list

Signed-off-by: o_koeh01 <o_koeh01@uni-muenster.de>