Re-implement sequences as macro in a module

[xs5871]

Better macros. It's not super pretty, but it's good enough to be an improvement:

• It's a module. No unecessary code in core.
• Asynchronous. Doesn't lock the entire firmware, but it will buffer key events when a macro is running and replay them afterwards.
• Clean Interface. No more awkward double negative no_press/no_release.
• Unittestable.
• Unintentionally flexible. Effectively any code can be put in a macro now.
• Spellchecked documentation on the third try.

I'll purge the abomination that's the sequences code soonish. A couple of board configurations need refactoring, which I'm not looking forward to.

[xs5871]

Sometimes clicking the right button is hard.

[anventia]

It seems like the docs have not been updated, and still shows the old Sequences, can this please be updated?

[claycooper]

New docs have been pushed to the website.