Update User Guide

[ArBridgeman]

Summary

This should be a light sprucing up, as we are preparing the beta-release.

⚠️ If more intense changes are requested/needed, then subsequent tickets should be made to be done after the beta-release but before the final release.

• Update user documentation
  • Add a page with connection parameters
  • Add a security page
  • Re-think the getting started page order to make it clearer
  • Add more explicit links to sqlalchemy & PyExasol

[ArBridgeman]

closed by #662