add set_basis_set method

[NilsHeunemann]

Adds a method to set the basis set for all types of calculation.

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Checklist

• [x] The changes include an associated explanation of how/why
• [x] Test pass
• [ ] Documentation has been updated
• [x] Changelog has been updated

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 97.45%. Comparing base (c9c2c2b) to head (3f512ae).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## v1.4.3 #330 +/- ## ========================================== + Coverage 97.42% 97.45% +0.03% ========================================== Files 209 209 Lines 23761 23768 +7 ========================================== + Hits 23148 23162 +14 + Misses 613 606 -7 ``` | [Flag](https://app.codecov.io/gh/duartegroup/autodE/pull/330/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=duartegroup) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/duartegroup/autodE/pull/330/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=duartegroup) | `97.45% <100.00%> (+0.03%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=duartegroup#carryforward-flags-in-the-pull-request-comment) to find out more.

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[t-young31]

what's the rational for being able to set the optimisation and single-point basis set to the same value? I'm not sure I can think of one!

[t-young31]

In the absence of a reply I'm going to close this. Feel free to reply and we can revisit!