Checklist items sort fix, and checklist sort capability.
Checklist items sort fix, and checklist sort capability.

Thanks to andresmanelli !

Closes #876, closes #1483, closes #1237

johnleeming/wekan,GhassenRjab/wekan,johnleeming/wekan,wekan/wekan,wekan/wekan,wekan/wekan,GhassenRjab/wekan,johnleeming/wekan,wekan/wekan,libreboard/libreboard,johnleeming/wekan,GhassenRjab/wekan,libreboard/libreboard,wekan/wekan