Portpy

1. Visualization.py: dose > 0 criteria removed for visualization
2. influence_matrix.py: Down-sampling beamlets when removing corner beamlets

1. Resolving python rounding issue. Use ceil instead of round for step size change
2. Modified beams.py so that beam ids can take integer or string values
3. Minor updates in examples

1. Added notebooks for a. VMAT SCP based dose prediction pipeline. b. VMAT SCP plan import to TPS
2. Modified examples directory structure and filenames.
3. Added methods in vmat_scp for dose prediction pipeline
4. Fixed bug in predict_using_model() method in portpy.ai module.

1. Added module SCP based VMAT optimization (PortPy.Photon.VmatScp)
2. Bug fixes related to evaluation and visualization of plan
3. Added example for SCP based VMAT opt
4. Added feature for creating rt plan DICOM file for PortPy VMAT plan, which can be further imported to any TPS

Fix Evaluation.py display_clinical_criteria() for displaying all type of dvh constraints

Patch release. Fix bug in influence_matrix.py and structures.py.