Haxe 3 Support

This release

- adds support for Haxe 3 RC
- removes support for Haxe 2.08 and 2.09
- remaps `massive.neko.*` to `massive.sys.*` to align with haxe conventions
- removes `allClasses` command from mlib tool
- updates source folder strucutre and build scripts to work with haxelib dev and haxelib git