Add 'releaseCodeOptimization' argument option

[chrisyarbrough]

This PR adds the Unity editor command line option releaseCodeOptimization which disables debugging support in favor of optimized C# code. This option makes sense on dedicated build machines where debugging is usually not performed and the editor is used for long-running tasks such as running tests or performing AssetDatabase operations. In these situations it can be a speed improvement to use release-mode code.