GSH templates support input type of 'find a Subject' and 'find list of Subjects' types

It would be helpful to reuse the existing 'add Member' UI structure and logic to allow a user to select a subject ( or a list of subjects) as an input to a GSH template.

Ideally the GSH template config could also add some limits/scopes to the searches too:

• check boxes for the subject sources to search 
• Maybe a "stem scope" would be helpful too ( for finding folders/groups )
• It would be useful to be able to use the "gsh_builtin_*" values in this process too.
• It would be useful to be able to use the "gsh_input_*" values in this process too.