Review spec systems

[schomatis]

• node types: https://github.com/filecoin-project/specs/blob/master/src/systems/filecoin_nodes/node_types/node_types.md

• IPLD store: https://github.com/filecoin-project/specs/blame/master/src/systems/filecoin_nodes/repository/ipldstore/_index.md#L19

• update libp2p spec links (like gossipsub): https://filecoin-project.github.io/specs/#systems__filecoin_nodes__network

• explain with human text the VM architecture (key part in the entire system): https://filecoin-project.github.io/specs/#systems__filecoin_vm

• explain with text all the major actors, for example: https://filecoin-project.github.io/specs/#systems__filecoin_vm__sysactors__init_actor

• sync actors list with the specs-actors repo, or link directly there: https://filecoin-project.github.io/specs/#systems__filecoin_vm__sysactors

[mishmosh]

Created individual issues for each one, so closing this. Thx @schomatis!