MACE 3D demo development

Created by: dyang37

Review and revise MACE 3D demo:

• Review and get group agreement on the MACE 3D demo interface and code structure. This includes:
  1. Design and implement configuration files and their associated interfaces. The goal is to eliminate hardcoding in the demo. The configuration files should specify arguments like data download url, file/output path, geometry/sinogram/recon parameters, and different types of arguments should be grouped in different configuration files.
  2. For the bottle cap dataset used in demo, increase the contrast of the phantom image so that it is sharp.
  3. Make sure that the default parameters result in good reconstruction for the 3D bottle cap example used in demo. a). We changed constant of auto_sigma_p from 1.0 to 2.0. Need to verify that this results in good 3D MACE reconstruction.
  4. Revise docstring and README file so that user knows how to modify configuration files as needed.