Move x11/kde-applications/kcalcore to devel/kf5/kcalendarcore

kcalendarcore formals kcalcore moved from KDE applications to KDE
framwork. Attached port based on kcalcore with additional changes:

- Rename to kcalendarcore
- libKF5CalendarCore bump
- @pkgpath x11/kde-applications/kcalcore and @conflict kcalcore-*
- Update tested:
kcalcore-18.12.0p0->kcalendarcore-5.68.0: ok

OK to import?

pkg_info:
Information for inst:kcalendarcore-5.68.0

Comment:
The KDE calendar access library

Description:
This library provides access to and handling of calendar data. It supports the
standard formats iCalendar and vCalendar and the group scheduling standard
iTIP.

Maintainer: Rafael Sadowski <rsadowski@openbsd.org>

WWW: https://projects.kde.org/projects/frameworks/kcalendarcore