SPDXID from file incorrectly parsed by rdf parser #246

When parsing a rdf file the SPDXID of a file contains the whole path to the spdxID in the graph.
For example converting the example file SPDXRdfExample.rdf to a .tag file leads to the following output:

# File

FileName: Jenna-2.6.3/jena-2.6.3-sources.jar
SPDXID: https://spdx.org/spdxdocs/spdx-example-444504E0-4F89-41D3-9A0C-0305E82C3301#SPDXRef-File1
FileType: ARCHIVE