Add modify function to test API helper
Add modify function to test API helper

The modify function is a generic function used to modify any part of any
object via the restful API.

j0gurt/ggrc-core,kr41/ggrc-core,AleksNeStu/ggrc-core,edofic/ggrc-core,AleksNeStu/ggrc-core,plamut/ggrc-core,josthkko/ggrc-core,selahssea/ggrc-core,andrei-karalionak/ggrc-core,selahssea/ggrc-core,prasannav7/ggrc-core,josthkko/ggrc-core,selahssea/ggrc-core,prasannav7/ggrc-core,prasannav7/ggrc-core,NejcZupec/ggrc-core,VinnieJohns/ggrc-core,kr41/ggrc-core,j0gurt/ggrc-core,kr41/ggrc-core,j0gurt/ggrc-core,edofic/ggrc-core,josthkko/ggrc-core,plamut/ggrc-core,kr41/ggrc-core,plamut/ggrc-core,VinnieJohns/ggrc-core,selahssea/ggrc-core,andrei-karalionak/ggrc-core,edofic/ggrc-core,AleksNeStu/ggrc-core,andrei-karalionak/ggrc-core,andrei-karalionak/ggrc-core,AleksNeStu/ggrc-core,edofic/ggrc-core,NejcZupec/ggrc-core,prasannav7/ggrc-core,josthkko/ggrc-core,NejcZupec/ggrc-core,j0gurt/ggrc-core,VinnieJohns/ggrc-core,VinnieJohns/ggrc-core,NejcZupec/ggrc-core,plamut/ggrc-core