Update task due notification template

* For each task past due, add link to task on kanboard if application_url is specified.
* Add task due date.
* Remove task link on footer.
Merge pull-request #356 (bugfix Helper\a())
Add Thai translation (pull-request #353)
Update contributors list
Rename Locales and Templates folders to be more consistent
Update contributor list
Update JsonRPC library
Change Vagrant config to have multiple boxes
Add pagination for users page