add forward_model for facilitating (s)3DXRD analysis

[haixing0a]

The aim is to exploit forward model for the following purposes:

1. facilitate analysis for (s)3DXRD by filtering and cleaning peaks for indexed grains, calculating completeness
2. bridging the combined analysis between DCT and (s)3DXRD for the same sample but measured in different geometries/instruments
3. forward model based reconstruction for both near-field and far-field geometries
4. parameters conversion among ImageD11 par, DCT parameters, poni, which all can be converted to a dictionary and compatible with fwd-DCT parameters
5. other auxillary tools for multi-modality analysis, including interacting with PCT, sample environment, orientation conversion, deformation analysis (schmidt factor calc) etc.
   A lot more is under development...