Missing support for relative URIs in relationships

[mconradi-iese]

The OPC format allows relative URIs in relationships, but the aasx-explorer doesn't load an .aasx if it contains a part URI that doesn't start with a forward slash.

We would like to use the Apache OPC library from the POI project in Eclipse BaSyx to build .aasx files. This library uses relative part URIs.
E.g. in the file /_rels/.rels it sets "aasx/aasx-origin" as target instead of "/aasx/aasx-origin" expected by the aasx-explorer.

I've generated a minimal .aasx file with the Apache OPC library test.zip (renamed .zip for GitHub to accept it). It loads if all relative paths in the .rels files are manually replaced by absolute paths. But I think it should also load with the relative paths.

I've tested it with the 2020-12-03 binaries.

[juileetikekar]

Hi @mconradi-iese,

The latest version of the package explorer consists of a fix for this issue and can open the file attached in the description.

similar to #146