dplyr v1.0.0 / vctrs todo

[mitchelloharawild]

Many changes are required to support the upcoming release of dplyr, these issues are consolidated here:

• Use progressr instead of dplyr::progress_estimated() Use progressr instead of dplyr::progress_estimated() #184
• Improve dplyr methods for mable objects Improve dplyr methods for mable objects #179
• Automatically select() key variables in a mable Automatically select() key variables in a mable #170
• Add support for join operations Add support for join operations #161
• Add ggplot2 scales for agg_key structure Add ggplot2 scales for agg_key structure #141
• Add multivariate functionality back with new distribution structures