SolverEngines v3.0 for KSP 1.2.2

• Update for KSP 1.2.2
• Fix toolbar button not displaying
• Fix thrust and drag displays in GUI
• Fix fittable engines being fit every time even if they had no changes
• Breaking Change Refactor EngineThermodynamics to be a struct, which makes it easier to use without adding GC alloc
• Fix issue with negative mach transformations
• Breaking Change Streamline engine fitting code
• Only save fitted engine when parsing prefab, this prevents part upgrades from affecting the cache (however, upgraded parts will have to be fit every time)