This MR adds the adapter.aasx module with AASXReader and AASXWriter classes to read and write .aasx files according to DotAAS section 7. Fixes #38 (closed).
It also adds/changes some core functionality to make this possible (or make testing easier):
New module aas.util.traversal for traversing AAS object structures
Improved DictObjectStore.__init__()
Fixing paths in test.compliance_tool for unixoid systems
Add Submodel references for identification and BOM submodels to Test_AssetAdministrationShell in examples.data.example_aas
