Multiline version_locations

**Describe the use case**
When there are many version locations it becomes difficult to read the value of the version_locations option. A new option "newline" for version_path_separator is suggested.

**Example Use**
```
version_locations =
  /foo/versions
  /bar/versions
  /baz/versions

version_path_separator = newline
```

**Have a nice day!**
