added stubs for voxel merge methods
implemented merge setters
using cropped shape explicity for merged shape calculations
default config is not merged
override voxel size if merged
cropped shape is always the correct shape
if merged return corrected shape
fixed get shape method if merged
fixed spacing method if merged, un-re-named GetVolumeShape
moved index unpacker from HDF5 derived class to G4VoxelArray
implemented index unpacker for row major
added merge size getter
changed return type to std::vector<unsigned int>
correct index for merging
abstracted rounding method
preliminary support for placing merged parameterisations