Better interface for options

[Craftplacer]

sane.dart should provide easy access to well known options, and make it natural to access options.

Goals:

• Use subscript access for option number / name, getting and setting (null as value for auto config?)

Non goals:

• Interpreting and managing not well-known options (out of scope)

Concept:

device.options.scanArea.x = 20;
device.options['source'] = 'Flatbed whatever';

[Jupi007]

Also, I really don't like the current _controlOption() implementation...
We could replace the generic control options with getOption<T>(), setOption<T>(), setAutoOption<T>(), controlButtonOption().
The biggest problem is working with value type...