WIP: Added dev.md file to container-loader

[WayneFerrao]

Thought it would be a good to start a dev.md document which would serve as a readable guide to bring a new engineer up to speed on these nuanced areas of the codebase. Far from complete, I started by adding my consolidated understanding of what goes on when clients connect and disconnect from the server, while working on AB#659

I'm trying to keep the document informative but not too granular in detail to prevent the need to be updated often.

Please feel free to make corrections and suggestions.