Merge remote-tracking branch 'bills/master' into fix_issue_26_add_SagPlateDilution
updating this branch with the bills/master
Correcting the error shown when trying to add a new SAG plate dilution.
This error was shown because the class SAGPlateDilution doesn't have any extracted_cell attribute
group_id_keyword='sag_plate__extracted_cell__sample__id' istead of group_id_keyword='extracted_cell__sample__id'
Merge pull request #28 from felixeye/master

Add SAG plate dilution gives error fix #26