Add support for model version

[amcadmus]

• Model version in format MODEL_VERSION_MAJOR.MODEL_VERSION_MINOR
• Implemented in both c++ and python interfaced
• Disentangle DeepPot from DeepTensor. DeepTensor may become a base class of DeepPot when the model is better designed.
• Use model_attr/output_dim to determine the output dimension when inferring DeepTensor

[codecov-io]

Codecov Report

Merging #418 (91971a2) into api (3bd863b) will increase coverage by 0.24%.
The diff coverage is 94.23%.

@@            Coverage Diff             @@
##              api     #418      +/-   ##
==========================================
+ Coverage   60.09%   60.34%   +0.24%     
==========================================
  Files          65       66       +1     
  Lines        5157     5202      +45     
==========================================
+ Hits         3099     3139      +40     
- Misses       2058     2063       +5     

Impacted Files	Coverage Δ
deepmd/entrypoints/freeze.py	19.56% <ø> (ø)
deepmd/infer/deep_eval.py	96.90% <91.30%> (-1.50%)	⬇️
deepmd/infer/deep_tensor.py	93.10% <93.10%> (ø)
deepmd/infer/deep_dipole.py	75.00% <100.00%> (ø)
deepmd/infer/deep_polar.py	65.21% <100.00%> (ø)
deepmd/infer/deep_pot.py	68.78% <100.00%> (+3.29%)	⬆️
deepmd/infer/deep_wfc.py	58.33% <100.00%> (ø)

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[amcadmus]

• Disentangle DeepPot from DeepTensor. DeepTensor may become a base class of DeepPot when the model is better designed.

@marian-code please note the above change

[marian-code]

• Disentangle DeepPot from DeepTensor. DeepTensor may become a base class of DeepPot when the model is better designed.

@marian-code please note the above change

Thanks for the heads up! I have been preoccupied with other things so I haven't been able to contribute anything for the last weeks.