RT ECS docs rewrite

[benev0]

This rewrite of the ECS doc has the goal of simplifying explanations of the architecture pattern.

• split the document into atomic parts
• remove and replace composition over inheritance diatribe (needed for DM programmers)
• provide minor edits to current quality content (event patterns)

fix #15

[benev0]

I need to revisit FAQ.

[benev0]

The system example does not have a update system in it.

[benev0]

Added update to code example, but it may be worth splitting the sample up so that it is present adjacent to each of the appropriate sections. seeking opinions.

I would appreciate a read through by someone who is not me. If you find something that is difficult to read, verbose, incorrect, or flawed, then feel free to mark it with anything from "here" or "this" to a detailed explanation of an issue. The latter is preferred for incorrect technical information.

If you do not understand ECS concepts before reading and do not understand during or after reading, your review is very valuable to me, so please post your review. The goal is to bring you up to speed on ECS; you are the target audience.