Extend Test Module Documentation & Explain Python integration

- Extended the openQA Test Module documentation with improved
  structure and examples.

  The module interface is documented (all the possible routines and
  their purpose are explained & trackable in the sidebar).

- Explained how the python support works in openQA.

  Added a small section on how python support is provided by
  openQA, as well as the limitations that 'Inline::Perl' brings.

- Reorganized the example test modules.

- Perl-tidy'd perl examples.

Co-authored-by: Liv Dywan <[email protected]>
Co-authored-by: Martchus <[email protected]>
Co-authored-by: Oliver Kurz <[email protected]>