Opencraft v3 - Core changes compared to v2

This is the main PR for the organizational changes being presented for OpenCraft v3.

http://opencraft.com/doc/handbook/

Before going to read the PR, I recommend to read the first 3 pages from the generated version linked above, until “Organization”, included.

See detailed description, other related PRs and the recommended order to review these on the main forum post: https://forum.opencraft.com/t/opencraft-v3-scaling-up-some-self-management/141