Integration with iCloud

## What? Why?
Integration of SugarRecord with iCloud allowing the user to initialize the stack ready to work with iCloud

## What should be tested?
iCloud synchronization with the local store works

## Related tasks? 
No related task

New feature that allows the user to start the stack linked to iCloud
https://github.com/magicalpanda/MagicalRecord/search?utf8=%E2%9C%93&q=MR_coordinatorWithiCloudContainerID

![gif](http://media.giphy.com/media/Zg2Y4b799fp1C/giphy.gif)
remember class methods also in this file