v0.22: Hot-reloadable programs, 3D variants

There is now support for Transform2D, Transform3D, Basis and Quaternion. Some Variants can be now in-place updated, including permanent ones. And finally, if a program is updated it will be reloaded in the editor, including its properties. Property values are retained across updates.

• Added Variant::make_permanent() to promote/move a temporary variant into permanent storage
• Some Variants can now be in-place updated, including permanent ones
• Improved error messaging around Variants and Objects
• Hot-reloadable Sandboxes with preserved Sandbox property values
• Introduce wrappers and several methods for Transform2D, Transform3D, Basis and Quaternion
• Implement several new methods for Vector2
• Add use_precise_simulation property to Sandbox for the purposes of debugging exceptions
• Add new experimental binary translation option automatic N-bit address space, which improves performance but won't support all types of programs

What's Changed

• Add initial support for Transform2D, Transform3D and Basis by @fwsGonzo in #172
• Add support for in-place reuse of Variant references by @fwsGonzo in #173
• Reload sandboxes when ELF files change by @fwsGonzo in #174

Full Changelog: v0.21...v0.22