Remove fWriter pointer from JPetTask
Remove fWriter pointer from JPetTask

alexkernphysiker/j-pet-framework,alexkernphysiker/j-pet-framework,JPETTomography/j-pet-framework,wkrzemien/j-pet-framework,JPETTomography/j-pet-framework,alexkernphysiker/j-pet-framework,wkrzemien/j-pet-framework,alexkernphysiker/j-pet-framework,wkrzemien/j-pet-framework,wkrzemien/j-pet-framework,wkrzemien/j-pet-framework,JPETTomography/j-pet-framework,alexkernphysiker/j-pet-framework