Add RV Plots

[vandalt]

These functions should be accessible from API and CLI:

• Full RV timeseries optionally with components (planets, trends, GPs) and envelope (if sampling was done) and residuals in extra panel
• Phase-folded RVs for each planet with residuals and epoch coloring
• Trace plots
• Corner plot
• Tweak RV plots to make more flexible (colors, remove parts, etc)