added DoesNotExistError class
Merge branch 'master' into sales_purchase_return
raise custom validation in validate_value of controller, removed unused event method and ability to return more docs to client in webnotes.response['docs']
Merge branch 'master' of github.com:webnotes/wnframework into sales_purchase_return
email saving fixed.
Merge branch 'master' of https://github.com/webnotes/wnframework