Make KOrganizer and friends prettier.

1. Update icon names for missing icons:

recur -> task-recurring or appointment-recurring
bell -> task-reminder or appointment-reminder
checkedbox -> task-complete
organizer -> meeting-organizer
groupeventtentative -> meeting-attending-tentative
groupevent -> meeting-attending (OK???)
month -> view-calendar-month

(description of the icons: <a href="http://techbase.kde.org/index.php?title=Projects/Oxygen/Missing_Icons">http://techbase.kde.org/index.php?title=Projects/Oxygen/Missing_Icons</a>;)

2. add missing icons (copies of appropriate oxygen icons)

The icons are put into share/apps/kdepim/icons/, a place where icons shared by many apps could go.

Most of the icons will go to oxygen set itself when artists finish their work.

3. KOrganizer: Fix vertical positioning of icons like the 'reminder' within the appointment items.