Feature to help merge a new document into an existing multi-form interview

[miabonardi]

When working on multiform projects, there are repetitive steps to add a new form and it would be great/super cool if we could upload the existing multiform project to the weaver and then also upload the new file to add and have the weaver integrate the new template into the multiform project. This would ideally include:

1. Adding the new file to the al_user_bundle
2. Adding the new file as a selection from the list of documents included in the multiform project (main interview order), place the sub interview order complete here and direct to interview order in sub yml specific to new uploaded template
3. Add attachment blocks to sub yml specific to new uploaded template
4. Add new variables from template to interview order of sub yml specific to new uploaded template

[nonprofittechy]

See also #892

[VTskier]

I could use this right now. Sounds great!