Merge Porch documentation to kpt

[CsatariGergely]

Render the two documentation in a way that the Porch documentation is an integral part of the kpt documentation.

How to organize the source files of the Porch documentation is open

• Move to the kpt repo (or a docs repo :))
  • More easy for a "natural" integration of the two documentation
  • Removes the connection between the code and the documentation in the same repo
• Keep it in the Porch repo
  • Needs some hack to get the files to their correct place when the kpt documentation is rendered. We need to be able to trigger the render when the Porch documentation is changing