Support `refit = FALSE` in `get_feature_paths`

[michaelweylandt]

Path plots use the get_feature_paths interface to access raw features
and principal components in a unified way for plotting. This seems to produce
some jumpiness that might be resolved by supporting a refit = FALSE option
similar to what we do for get_clustered_data as used by heatmap plots.

• Determine if refit = T/F explains coarseness of feature plots
• Add refit support to get_feature_paths
• Pipe refit argument through path plots