sdf::addURIPath does not work in windows

The code in `sdf::addURIPath` assumes the `:` delimiter is used to separate multiple paths, but in windows, this delimiter is used in individual paths to indicate the drive letter (eg. `C:/path/to/file`). According to [this windows documentation](https://docs.microsoft.com/en-us/previous-versions/aa922003(v=msdn.10)?redirectedfrom=MSDN), the semi-colon should be used as the delimiter instead of the colon.
https://github.com/osrf/sdformat/blob/fc4dc8c74006074a918f59e81ca1148c38198edc/src/SDF.cc#L177-L192

Start in src/SDF.cc at sdf::addURIPath, using the linked lines as the entry point. Check how path lists are split on Windows versus other platforms, then verify that drive-letter paths remain intact and multiple paths use the documented delimiter.

Written by the indexing model from the issue text.