Restructure ARM

Major restructuring of the ARM.

It consists of several changes:

• Structural changes - chapters were reordered
• New introduction to config - it was completely rewritten
• New description of how to use RPZ

Please note individual commits do not build successfully. This is a known problem and is left intentionally unfixed as fixing it would be uneconomical - this merge is condensed from 260+ individual (and messy) commits.

Related: #3169