Updates post committee-draft (work in progress)

What's Changed

• Meeting 30 sep by @thclark in #115
• Clarify and unify design_lifetime into single field by @thclark in #118
• Define thust and power as non dimensional / dimensional always by @thclark in #119
• FEA: Update cut kind to cut_type by @thclark in #124
• Rename sound_pressure_level to sound_power_level by @thclark in #127
• De-requirements: Make things that can be empty anyway optional by @thclark in #128

Full Changelog: 1.0.0.alpha-2...1.0.0.alpha-3