Feature/pk tweaks

[helixhorned]

Various usability tweaks. (In my opinion enhancements, of course, but your mileage may vary.)

I'm not yet very happy that the now-local history list is not persisted, but then maybe it is of not much practical relevance as the few Unicode blocks you're working with regularly are presumably easily remembered. Time will tell.

I'm sorry if charmap-enable-simple is present for a future feature (just looked at the issues list).
As a matter of rule I remove everything unused from code I work with, but of course that commit can be easily dropped if the variable is intended to stay.

EDIT: builds based on feature/update-to-blocks-13.0.0 (PR #12); I created two pull request because I expect this one to be potentially controversial.

[helixhorned]

Rebased; updated my email address.

[lateau]

@helixhorned Hello, Are you still using Emacs?

[helixhorned]

Hello @lateau! Yes, I am. And charmap is a core package to me, meaning that I integrate it into my private Emacs configuration Git repo.