Restore postponed tasks after the postpone period has elapsed
Show remaining postponed time for postponed tasks
Fix TaskAdapter filtering

DBQuery generates the sql each time from string fragments so we can
switch some where clauses on the fly
Period has now second resolution, fix restoring postponed tasks
Uncheck all tasks after postpoining a task
Run postpone restore routing in a timer
More verbose button texts
Do not show postponed dialog if no tasks are selected
Fix indentation
Put nil in db if values are None in Task instances
Add OneMinute period for testing purposes
Add default case matching in task json serialization
Migrate db
Start/stop the timer on activity resume/pause
Merge branch 'feature/fix-repeating-tasks' into dev

* feature/fix-repeating-tasks:
  Start/stop the timer on activity resume/pause
  Migrate db
  Add default case matching in task json serialization
  Add OneMinute period for testing purposes
  Put nil in db if values are None in Task instances
  Fix indentation