Initial commit of Longitudinal PET/CT Analysis Extension V.02

DICOM Plugin updates:
- DICOMLoadable caching for performance improvement
- Selection from multiple CTs for PET
- PET only support
- Usage of PETSUVImageMaker module to generate normalized volumes

Module updates:
- Registration of PET/CT studies image volumes
- Module settings sidebar
- PET color selection presets
- CT Window/Level selection presets
- ReportOverview Table provides statistics in cells
- Additional segmentation statistics: StdDev, Count, Volcc, Volmm3