Section 9: Clarify pre-release definition

- Remove confusing 'satisfies' usage.
- Specify that pre-release identifiers cannot be empty.
Section 11: A larger set of pre-release is higher

Clarifies the comparison between, eg 1.0.0-a vs 1.0.0-a.b
Section 11: Clarify left-to-right comparison
Add 'Parsing Logic' pseudocode
Add 'Precedence' pseudocode