port onchanges to API 8.0 to fix #22
Add a second search when no agreement is found

This restore former warning message when we can find an agreement with
not enough quantities
This allow to find and finish the framework agreement almost finished.
As it is preferable to finish agreements completely instead of
contracting new ones and be left with multiple remainings of agreements.
Merge pull request #23 from yvaucher/8.0-framework-agreement-sourcing-fix-onchanges

port onchanges to API 8.0 to fix #22