Store the actual archive when commit
* Registry: Use the size to have a good progress bar while pushing
* Registry: Use the actual archive if it exists in order to speed up the push
+ Registry: Remove the archive if it exists after the push
Refactor PushRepository to fix error 400 and to increase processing speed
Factorize the checksums functions
Improve the checksum process
Remove the pushImageRec and use iteration instead
Send the images in correct order
Fix error code message upon error on push
Merge pull request #568 from dotcloud/improve_checksum-2

* Runtime: Store the actual archive on commit
* Registry: Improve the checksum process
- Registry: Fix error 400 on push