change license to CC0 for notify and apache/mit for new crates

[0xpr03]

Closes #514

[0xpr03]

I'm inclined to change the debouncers to the MIT/Apache 2.0 dual license. It is the default for most crates and we still can change this for new stuff, as they're not that old.

cc @passcod @dfaust @decathorpe

[0xpr03]

ah come on bsd..

[decathorpe]

MIT OR Apache-2.0 would be OK from my point of view as well, but simplifying to CC0-1.0 first is a good idea regardless of the further steps.

[dfaust]

I'm fine with any of the licenses, CC0-1.0, MIT, and Apache-2.0.
Personally, would cast my vote for MIT, but then again, I'm not an expert in the field. So please do whatever you think is best.

[0xpr03]

If there are no objections, I'll merge this tomorrow.

[0xpr03]

last commit only moved the notify CC0 license into the notify folder