[traits.build adding studies functions] Merge some current {austraits} functions into {traits.build}

[ehwenk]

Merge some current {austraits} functions into {traits.build} to reduce package co-dependencies.

Need to review which functions should be moved, then move them.

[ehwenk]

I believe the only austraits.R function used in traits.build is extract_dataset is used in report_dataset.Rmd. While we could bypass extract_dataset using filter (separately for each table), the function being developed to create a single combined table does require join_contexts.

Therefore, we need to more broadly work out a plan for which functions will be part of which package.

[ehwenk]

We've actually decided to do the reverse and move functions back to austraits. report_dataset.Rmd will remain in traits.build, but the remaining functions, including the function to build a single combined table will move to austraits.