261 data objects

Fix #261 

It is built upon #257 since it needs thickbox modals to work.

I removed most of the code for `update_data_objects` action since they are doing irrelevant work by finding the active tasks, which is the same as what `active_task` action on tasks_controller does.

[See the compare](https://github.com/YaleSTC/shifts/compare/255_stickies...261_data_objects?w=1)