Fix links to AUR page and project website
Fix text in README pointing to online guides
Remove elaborate reference to the documentation

The README had a lot of deep links into the documentation. This made it
hard to maintain. Therefore, I removed all this with a simple reference
to the documentation. The main page of the documentation should be the
new landing page for users.
Reword documentation landing page
Integrate paragraphs from my personal homepage
Add more text from the website
Clean up legal section
Create separate developer documentation section
Fix typo
Paragraph break
Put unity launcher hook into main script
Sort config options alphabetically
Changelog entry
Fix typo
Explain what guessing means
Update manual page
Changelog entry