Improvements to Developer Starter Pack

[zhyatt]

Comments from community on https://docs.nano.org/node-implementation/contributing/#wip-developer-starter-pack

• One issue I have with it is the headers for different sections are inconsistent. Sometimes they are conceptual headers like "SIGNATURE CHECKER" and other times they refer more specifically to a class or object like "WRITE_DATABASE_QUEUE"
• And adding navigation the long list of node functions for the higher level categories like "BOOTSTRAPPING", similar to how "Voting/Consensus" shows up, but could use some more high level categories to separate/categorize the node functions at a higher level. Ideally connecting the living white paper to sections in this document would be helpful to get more conceptual details from the living whitepaper and then connect them to specific node functions through a link would be good

[zhyatt]

These items will be closed by https://github.com/nanocurrency/nano-docs/pull/559