Modify the behavior of compute fields for our computed fields used for criterias

[jeremi]

The addition of new computed fields on res.partners would be quite common in our system. So we need to make it easy to use. Right now, if you have a large amount of data, it often fails to install an app.

So we need to:

• Do not recompute additional fields when installing an app but store them to be run in a queue using Celery ( #1 )
• Recompute directly only if few records are impacted (Less than 10)
• Use celery to re-compute them