Change mission lists items' drawable when Trash icon selected/deselected

Closes https://github.com/DroidPlanner/droidplanner/issues/508

TODO:
- [ ] Fix drawable size


![screenshot_2014-07-31-13-48-47](https://cloud.githubusercontent.com/assets/3159171/3763967/af220346-18aa-11e4-96aa-4666ff5a9e90.png)
![screenshot_2014-07-31-13-48-51](https://cloud.githubusercontent.com/assets/3159171/3763968/af3f20fc-18aa-11e4-8161-b430582c19da.png)
@alextel69 Do we really want to save the DELETE state? If we are saving something it should be the selected tool, and from that change the state line in line 182.

I'm not sure if we even need to save the tool state, because it might be better to reset it when the user switch activities.