Add new study: Togashi_2015

[ehwenk]

• compilation of Huber value values from many resources
• some datasets exist in AusTraits as stand-alone datasets and these have been filtered out of Togashi
• remaining datasets also linked to their source_id's

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (9aa4f8c) 80.24% compared to head (232d015) 80.24%.

:exclamation: Current head 232d015 differs from pull request most recent head 17490e3. Consider uploading reports for the commit 17490e3 to get more accurate results

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #747 +/- ## ======================================== Coverage 80.24% 80.24% ======================================== Files 7 7 Lines 1534 1534 ======================================== Hits 1231 1231 Misses 303 303 ```

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