Summary:
For shared people's calendars on Kolab this code would lookup a matching
entry in LDAP directory to display the real name, and allow for showing
FB calendar. Since this only works with calendaring through Kolab
resource and the current recommended approach is to use DAV for
calendaring instead, we can remove this rarely-used code and simplify
the logic in CalendarView.

This also allow us to remove the KPIM::Person and related code from
libkdepim and finally drop collection referencing from Akonadi.

Test Plan: KOrganizer compiles, quick view still works.

Reviewers: vkrause

Reviewed By: vkrause

Subscribers: kde-pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D20344