This fixes a handful of links and standardizes the remaining links.
Redundant ToC titles were removed in two documents. Hotlinked
images have been added. README.md header image was optimized to a
tenth of the size. Images were moved into doc/Images directory.
Images generated using PlantUML had transparent backgrounds which made
their text difficult to read on GitHub when using "Dark Mode". Forcing
a background color of #F0F0F0 ensures they are all readable.
Updated development process description to reflect recent arrangments
within the team. The discussion was mostly on how many commits should be
included in a single PR but eventually it led to a general review of a
development process.
Removed outdated diagram.
