Add pre-push hook to disable pushing to upstream
Add pre-push hook to disable pushing to upstream

By default developers should not be able to push to upstream repo unless
they manually remove this hook. This is to prevent accidental pushes.

AleksNeStu/ggrc-core,andrei-karalionak/ggrc-core,selahssea/ggrc-core,VinnieJohns/ggrc-core,AleksNeStu/ggrc-core,VinnieJohns/ggrc-core,andrei-karalionak/ggrc-core,AleksNeStu/ggrc-core,andrei-karalionak/ggrc-core,andrei-karalionak/ggrc-core,selahssea/ggrc-core,VinnieJohns/ggrc-core,AleksNeStu/ggrc-core,VinnieJohns/ggrc-core,plamut/ggrc-core,plamut/ggrc-core,selahssea/ggrc-core,selahssea/ggrc-core,plamut/ggrc-core,plamut/ggrc-core