Add new filter syntax, prefixing with an "at sign"; i.e., `@...`, that
disables glob expansion, treating `*` and `?` wildcard characters as
literal characters.
In the GUI, change the restore file picker to prefix paths with `@`
when expanding a node to avoid mistaking literal `*` or `?` characters
for wildcards characters and triggering the following error:
```
Filter for list-folder-contents must be a path prefix with no wildcards Parameter name: filter
```
This fixes#4300.
Dean Ferreyra
5f94cc19a7