docs/source/compliance_tool: Remove cli from the autodocumentation since the documentation of it is already done by argparsing

aas.compliance_tool.cli: Extract the argparsing into a separate function to enable using it in the automatic documentation

This merge commit changes the project's license from Apache License 2.0
to a dual-licensing model, allow the user to choose either
Apache License 2.0 OR Eclipse Public License 2.0.

This change is reflected in the license header of each source file as
well as in the NOTICE and README.md files.

The license change has been signed off by all former and present authors
of the project:
- Sebastian Heppner <sebastian.heppner@plt.rwth-aachen.de>
- Torben Miny (b. Deppe) <t.miny@plt.rwth-aachen.de>
- Leon Möller <leon.moeller@plt.rwth-aachen.de>
- Michael Thies <m.thies@plt.rwth-aachen.de>

Create AASX reading/writing tutorial

Closes #69

See merge request !73

Fixes #69

Using license header template from Eclipse jetty project.

adapter.xml: Finally fix deserialization of empty <qualifier> tags

Closes #132

See merge request !72

Empty qualifier tags are allowed per the XSD schema and a frequently
used in XML documents created by the AASX Package Explorer (i.a. in AASX
package files).

Follow up to 516bf1e7, which tried to fix this, but only replaced the
KeyError with an IndexError.
Fixes #132