Make examples recognized by cargo

[SkiFire13]

#222 fixed the imports in the examples, however it didn't actually fix CI. The reason is that cargo doesn't recognize crate examples, only single files or a main.rs inside a single folder (not nested like in a crate). This PR fixes this by changing the file structure in such a way that cargo recognized them. Note that:

• I cargo fmts the examples because now that cargo can see them it can also format them. This wasn't the case before.
• I removed the cargo check --examples from CI because it is redundant: cargo test already checks them, but both commands require the file structure to be correct.
• I also updated the examples to use ConfigBuilder in order to fix the warnings. This might need some feedback here since I'm not 100% this is right.
• The config position relative to the main.rs is not accurate anymore unfortunately.

[matthiasbeyer]

Grml... I should've checked this more carefully! Thanks a lot for fixing this up!

[SkiFire13]

I've removed those #[allow(deprecated)], and although I don't really like the end result I don't think there are better ways with the current state of the crate.

[matthiasbeyer]

Superceeded by #253