Post-release cleanup

[stigrj]

• cherry-pick documentation changes from release/1.1
• bump development version number to 1.2.0-alpha

[codecov[bot]]

Codecov Report

Base: 68.40% // Head: 68.40% // No change to project coverage :thumbsup:

Coverage data is based on head (4416784) compared to base (77d69f4). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #425 +/- ## ======================================= Coverage 68.40% 68.40% ======================================= Files 183 183 Lines 15477 15477 ======================================= Hits 10587 10587 Misses 4890 4890 ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=MRChemSoft). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=MRChemSoft)

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