Change examples to use Selector.with(payload) instead of Command::new()

[arthmis]

It seems it wouldn't be idiomatic? druid to use Command::new() directly and users should be pushed to use Selector to create commands. Currently the examples use Command new, so it would be nice to change any uses of Command::new() to MySelector.with(). Is this right? @cmyr

old way:

    const ExampleSelector: Selector<u64> = Selector::new("example-selector");
    Command::new(ExampleSelector, 45u64, Target::Auto);

now it should be

    const ExampleSelector: Selector<u64> = Selector::new("example-selector");
    ExampleSelector.with(45u64);

[cmyr]

Yes, I think this is the most ergonomic way to use these API. Thanks!

[arthmis]

Closed with #1761