Add functionality in mp/mps/mpo and add ExpDVR basis

[jjren]

1. support the addition of many mpos/mpss together. mps.add([mps1, mps2,....])
2. convertion between diagonal mpo and mps. Mpo.from_mps() Mps.from_mpo()
3. ExpDVR basis
4. add shift algorithm for excited states calculation ($H=H_0 + \sum_i \alpha_i |\psi_i><\psi_i|$).

[codecov[bot]]

Codecov Report

Patch coverage: 66.66% and project coverage change: -0.50% :warning:

Comparison is base (9583324) 84.79% compared to head (2236e71) 84.30%. Report is 1 commits behind head on master.

:exclamation: Current head 2236e71 differs from pull request most recent head d49fdae. Consider uploading reports for the commit d49fdae to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #155 +/- ## ========================================== - Coverage 84.79% 84.30% -0.50% ========================================== Files 105 105 Lines 10183 10355 +172 ========================================== + Hits 8635 8730 +95 - Misses 1548 1625 +77 ``` | [Files Changed](https://app.codecov.io/gh/shuaigroup/Renormalizer/pull/155?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=shuaigroup) | Coverage Δ | | |---|---|---| | [renormalizer/mps/mps.py](https://app.codecov.io/gh/shuaigroup/Renormalizer/pull/155?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=shuaigroup#diff-cmVub3JtYWxpemVyL21wcy9tcHMucHk=) | `89.21% <27.58%> (-1.31%)` | :arrow_down: | | [renormalizer/model/basis.py](https://app.codecov.io/gh/shuaigroup/Renormalizer/pull/155?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=shuaigroup#diff-cmVub3JtYWxpemVyL21vZGVsL2Jhc2lzLnB5) | `80.81% <40.19%> (-7.96%)` | :arrow_down: | | [renormalizer/mps/mpo.py](https://app.codecov.io/gh/shuaigroup/Renormalizer/pull/155?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=shuaigroup#diff-cmVub3JtYWxpemVyL21wcy9tcG8ucHk=) | `90.56% <84.61%> (-0.60%)` | :arrow_down: | | [renormalizer/mps/mp.py](https://app.codecov.io/gh/shuaigroup/Renormalizer/pull/155?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=shuaigroup#diff-cmVub3JtYWxpemVyL21wcy9tcC5weQ==) | `85.16% <95.00%> (+0.40%)` | :arrow_up: | | [renormalizer/mps/gs.py](https://app.codecov.io/gh/shuaigroup/Renormalizer/pull/155?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=shuaigroup#diff-cmVub3JtYWxpemVyL21wcy9ncy5weQ==) | `96.42% <100.00%> (+0.49%)` | :arrow_up: | | [renormalizer/mps/mpdm.py](https://app.codecov.io/gh/shuaigroup/Renormalizer/pull/155?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=shuaigroup#diff-cmVub3JtYWxpemVyL21wcy9tcGRtLnB5) | `88.46% <100.00%> (-1.65%)` | :arrow_down: | | [renormalizer/mps/tests/test\_gs.py](https://app.codecov.io/gh/shuaigroup/Renormalizer/pull/155?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=shuaigroup#diff-cmVub3JtYWxpemVyL21wcy90ZXN0cy90ZXN0X2dzLnB5) | `100.00% <100.00%> (ø)` | | ... and [3 files with indirect coverage changes](https://app.codecov.io/gh/shuaigroup/Renormalizer/pull/155/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=shuaigroup)

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[liwt31]

The test coverage is too low currently - it seems easy to add a few tests for these new functions

[jjren]

I will add doc and tests later.

[jjren]

I close the PR now and will open it again when the new features for nuclear dynamics are ready.