Support multiple content types option in orange-dam:queue-content-by-type

Problem/Motivation

When scripting use of the `queue-content-by-type` command, there is an option flag `--type` which allows the type to be scripted. In many cases, one may wish to queue more than one type.

While it's pretty easy to work around this with some shell constructs like so:

```
for type in "Audio File" "Encyclical" "Book"; do
drush orange-dam:queue-content-by-type --type="$type"
done
```

this requires 1) use of a shell script or shell function and 2) a fair amount of experience with shell scripting, and 3) That the names of the content types are easily escaped.

Migration command options support "multiple" items in its flags (such as idlist) via a comma separation `explode(',', $option)`. It would be a nice-to-have to do this for this command too.