[mkcal] Fix broken indentation and whitespace
[mkcal] Fix warning for unused parameter
[mkcal] Avoid binding NULL as int
[mkcal] Save end date as +1 for all day events, remove same when reading

All day events are defined to be inclusive of ending time.

Previously saving all day event without ending time made sqlite backend
do addDays(1) which, in effect, made the event two day.
Then again explicitly setting end time to same day as start didn't work
either because reading required ending after start.

The approach here should be compatible with events incorrectly written
with previous version.

On negative side, it's still not possible to save event from midnight
to midnight without turning into all-day.
[mkcal] basic test for all day events
[mkcal] read event times with no timezone as clock time

Currently KDateTime::ClockTime is saved into Sqlite as that time in
current timezone. Reading such only works if timezone does not change.

Fix by assuming empty timezone as clock time, reading utc value and
changing spec to clock time. Thus clock time saved in one timezone
will be read as same time for every other timezone, too.