Added unretire class method to Concept model
Added unretire class method to Concept model

hevalberknevruz/oclapi,burakince/oclapi,hevalberknevruz/oclapi,emrah-b/oclapi,burakince/oclapi,emrah-b/oclapi,OpenConceptLab/oclapi,ayseyo/oclapi,emrah-b/oclapi,molgun/oclapi,ayseyo/oclapi,ayseyo/oclapi,OpenConceptLab/oclapi,OpenConceptLab/oclapi,hevalberknevruz/oclapi,snyaggarwal/oclapi,molgun/oclapi,molgun/oclapi,hevalberknevruz/oclapi,OpenConceptLab/oclapi,emrah-b/oclapi,snyaggarwal/oclapi,snyaggarwal/oclapi,OpenConceptLab/oclapi,snyaggarwal/oclapi,burakince/oclapi,ayseyo/oclapi,molgun/oclapi,burakince/oclapi