fix(plot_spawning_biomass): Remove complications

Just have a standard plot and not all the if else statements by using
simple ifelse statements in the code. Also, removed plots for non-standard
output per Sam's guidance.

* There was a problem with `if(any(grepl("target", output$label)))` because it
  ignored what the user specified in `ref_line` if target is present in label,
  i.e., you could never get to MSY. There should be a two-level check, i.e.,
  what does the user want and is it present. I have not fixed this latter
  problem.
* Fixed use of `..., ]$estimate` to `..., "estimate"]` because you should not
  use the dollar sign which allows for partial matches.
* Use `switch()` statements instead of nested `if` `else` statements. Actually,
  now the function is so simple that I do not even have any switch statements
  but they can be helpful instead of nested if else statements.
* Fixed the non-relative plots to truncate data to only use years less than end_yr
* Some of the scaled items were hard-coded to 1000 instead of using scale_amount
* Removed show_warnings because it was not actually doing anything
* Use end_year rather than renaming it to endyr
* Subset sb to end year before determining the correct number of breaks
* MSY does not work so I removed it from the default reference list, only
  target and unfished work
* Need to fix:
  * units are not divided by scale amount to create new unit label
  * Why do we think that our determination of breaks is better than what ggplot2
    provides?
  * There is no example

DESCRIPTION

@@ -24,6 +24,7 @@ Imports:
     dplyr,
     flextable,
     ggplot2,
+    glue,
     naniar,
     nmfspalette,
     stringr,

R/plot_recruitment.R

@@ -1,6 +1,7 @@
 #' Plot Recruitment
 #'
-#' @inheritParams plot_recruitment
+#' @param dat A path to a file name where the data are stored.
+#' @param model The model type, to be deprecated.
 #' @param params Print/export the parameters of the stock recruitment function?
 #' @param params_only Only export the stock recruitment function or both the parameters and the plot(s)?
 #' @param units If units are not available in the output file, in metric tons,