Add calculator example.
Add platform indipendent console log.

start orbtk on wasm.

Resolve "subcrate - shell"

See merge request redox-os/orbtk!110

shell crate.

backend / window shell. Start reimplemenation of shell events.

backend / window shell.

Resolve "Window"

See merge request redox-os/orbtk!109

struct to window widget.

Move structs tests to files.

Start: Split orbtk into stand alone sub crates

See merge request redox-os/orbtk!108