WIP transitions refactor. medic/medic-webapp#714

Put transitions in async.series, apply transition changes to change.doc, save
at the end only if we have a true value in results array.

Warning: deprecated transitions `repeatable` property, todo remove them
from existing transitions. Transitions should be repeateable without
adverse effects.

Updated transition to return true value when doc is changed, deprected use of:

```
return callback(null, false);
```