Add button to insert remaining tasks

See https://drupal.org/node/2236363.

Tested Chrome and Firefox, I was unable to test Safari for some reason:

```
grunt build:safari
Running "exec:build_safari_ext" (exec) task
>> Exited with code: 127.
>> Unable to create release/safari/dreditor.safariextension
Warning: Task "exec:build_safari_ext" failed. Use --force to continue.

Aborted due to warnings.
```