Add form validation to eliminate duplicate partnerships of same type
Add form validation to eliminate duplicate partnerships of same type

Extend RSR_PartnershipInlineFormFormSet.clean() to include checking if an
organisation is has duplicate partnerships of the same partner_type and
complain if that is the case

[Fix #35]

akvo/akvo-rsr,akvo/akvo-rsr,akvo/akvo-rsr,akvo/akvo-rsr