start and size of ptm islands

src/grouping/ptm/ptmisland.cpp

src/grouping/ptm/ptmisland.h

src/grouping/ptm/ptmislandgroup.cpp

src/gui/ptm_island_list_view/ptmislandtablemodel.cpp

src/gui/ptm_island_list_view/ptmislandtablemodel.h

src/utils/types.h