Add tasks

Add tasks module.
New feature
+ PI can add a task
+ PI can edit task
+ Members can apply for task
+ PI can change member status
+ TaskMembers can upload files
+ Some testing
+ First draft for admin interface.

Changes
+ Added jQuery UI (for datepicker)
+ Improved Globalize.js
+ Extended Ember Data DRF2 adapter for (de)serializing 'date'

Reworked how ProjectWallPosts are loaded (because they're now in an outlet).