Improved documentation

[sgdavis1]

We need to improve the system architecture and data modeling documentation.

Currently the Sequelize models are relatively easy to find and parse, because the code is well organized and centralized by nature. However, I would like a little more detailed description of several components of this project:

1. The total system architecture (probably using Whimsical.com)
2. The data models retained in memory by the large system.js construct

Until we introduce Typescript ( #92 ), it will be very important to have these items better described and up-to-date to ensure consistency across the system. It will also hopefully help us identify places to improve code architecture and modularity if we have a high-level document and diagram of the current system available for discussions.