Add an argument that will allow the user to choose to the names of the analysis varaibles in a column or in the column name

[mbcann01]

The current behavior is to have the names of the analysis variables in a column and use generic column names like "row_var" and "col_var". This is usually the behavior I want because it makes it easy to combine multiple results tables into a single table for presentation (e.g. Table 1). However, there are times (e.g., when passing results to ggplot) that it can be useful to have the analysis variable as the column name containing its categories.

Sun Study example:

map_student %>% 
  # Complete case analysis
  filter(!is.na(ss_application_f)) %>% 
  freq_table(period_f, ss_application_f) %>% 
  rename(period = row_cat, ss_application = col_cat) %>% 
  select(period, ss_application, percent_row) %>% 
  ggplot(aes(period, percent_row)) +
    geom_point()