Option to write output to different directory than app working directory

[e-perl-NOAA]

Add option to choose directory to write output to that is different than the app's working directory scenarios folder because people in SE (@AdyanRios-NOAA) using SAC tool want to push to a private repo and you can’t change the repo settings of a forked repo (they want to be able to keep their SAC tool up to date with the current tool without having to download). This will probably look like still requiring people to have a scenarios subfolder in whatever new/other directory that they wish to write to.

Alternatively, it could also just have a text box for people to copy/paste the path to the directory (more opportunity for errors if people put the path in wrong or don't understand what that option is for, but a quicker/easier solution in the short term).

@e-perl-NOAA can work on this as it requires the shinyDirButton and shinyDirChoose which she needs to fix to write properly to bookmarks for the rest of the files from a previous pull request that didn't work properly.