[traits.build adding studies functions] enchancements to move_values_to_new_trait function

[ehwenk]

The function move_values_to_new_trait has two tweaks required to be cleaner.

First, it currently requires that we have a separate line of code before running the trait, that creates a new trait, as in

mutate(new_trait = NA_character_)

I haven't succeeded in coding this into the function. It needs to go in together with a T/F argument, that defaults to adding this line, but it could call upon an existing trait. For instance there are times where some values are mapped across to an existing trait.

Second, there is a problem is you have a string of values that includes an NA. This will occur if you want to leave the original trait value column with blanks. For I use "" in the list, as in c("parasitic", "", "saprophyte"), but this shows up as a blank column in the excluded data table. I tried adding an na_if line at the end of the function,

data[[original_trait]] = ifelse(data[[original_trait]] == "", NA, data[[original_trait]])

but it isn't working.

[ehwenk]

And third, we should incorporate the "to lower case" function as part of this.