rain 0.3.2

Minor improvements and fixes

• Use patchwork for ethnicity plot.
• In /R/compute_pca.R,
  • fix a missplaced .data pronoun.
  • core code rewrite.
• In /R/pca_report.R, add packages prefix for tidyselect.
• Remove gcta64 from system requirements.
• Remove dependency to R.utils.