Add documentation on parsing life cycle and hooks

[shadowspawn]

Pull Request

Problem

It can be hard to work out where to plugin extra functionality using the hooks. A specific example is reading configuration files.

See: #1843

Perhaps the full life cycle of executing commands should be documented.

See also: #1762 #1787 (comment)

Solution

Add a separate description of the processing life cycles and where the hooks fit in. This will be useful when discussions come up about adding more parsing affected hooks, and thinking about where config files can fit in.

[abetomo]

👍

[shadowspawn]

Shipped in 10.0.1