more pivot errors fixed

[ehwenk]

more fixes to pivoting problems:

• minor changes copied from traits.build back to austraits.build process.R file
• had to add locations to Yang_2023
• Witkowski_1991 would only recognised plant ages when I wrote them in letters; tried many many other tricks

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (0f0e751) 79.52% compared to head (7461553) 79.52%.

:exclamation: Current head 7461553 differs from pull request most recent head ef35535. Consider uploading reports for the commit ef35535 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #765 +/- ## ======================================== Coverage 79.52% 79.52% ======================================== Files 7 7 Lines 1548 1548 ======================================== Hits 1231 1231 Misses 317 317 ``` | [Files Changed](https://app.codecov.io/gh/traitecoevo/austraits.build/pull/765?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=traitecoevo) | Coverage Δ | | |---|---|---| | [R/process.R](https://app.codecov.io/gh/traitecoevo/austraits.build/pull/765?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=traitecoevo#diff-Ui9wcm9jZXNzLlI=) | `91.85% <100.00%> (ø)` | |

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