Cleanup all current APIs to mark stable for 1.0.0

[dreampiggy]

This is the main proposal for 1.0.0 milesone

[dreampiggy]

Current 0.x.y, match the Dart semversion.

Which means, each minor version may or may not break APIs. But any patch version does not.

In 1.0.0, any patch or minor version will never break APIs.