Clear the session on setup start

The migration stores some values in the session, which causes a failed migration
to start from the point where it failed after a cleaned database. This can only
be fixed by clearing the session.
Rename projects with the same name under the same parent in migrations

We enforce unique project names under the same parent project since a few
versions via a database constraint.
fix the deletion handling and structure
stop migrating todos
stop migrating nodes
stop migrating filemanager entries
stop migrating contacts
stop migrating helpdesk entries
Stop migrating calendars

We just keep the module because we need some of the code, we don't really
provide a calendar any more.
Remove jsonMonthList

jsonMonthList is only used by the deactived and unused legacy
Timecard and therefore not needed anymore.
Add a dark overlay to days in the future
Calculate overtime only till today
Always convert dates not just for default values
Exclude date times and convert them properly
Merge pull request #371 from dsp/darkOverlay

Dark Overlay for days in the future