Add command-log layer: logs key strokes, commands

[bmag]

Uses command-log-mode package, useful for creating demos.

command-log-mode is a newer fork of mwe-log-commands with a cleaner code IMHO, so I think this PR can replace #2006.

@blinkd I based the description in README.org on the one you wrote in your PR, I hope you don't mind.

Currently the PR installs via Quelpa a fork (by me) that adds colors to command-log-mode, but if/when the fork is merged upstream I'll change the :location to install command-log-mode from Melpa.

The command-log is toggled by SPC a L.

Here's a picture:

[nixmaniack]

👍

[dcluna]

👍

[CestDiego]

This is very cool, I've been using keyfreq before, and never heard of this and this looks cooler. Do you have any special reason for this? Have you used keyfreq before? also, could you move this toggle be under the t prefix?

[bmag]

@CestDiego I thought about it as an application for logging key strokes, that's why I put it under a prefix, but I can be convinced otherwise. Did you have a specific key in mind?

[CestDiego]

Wait...this is an application... It thought this would be like keyfreq ... this is great! :) I love it and people can see what keybindings I'm tapping now when I pair program

[syl20bnr]

Excellent app, I would suggest to move it to Spacemacs layer and its doc to DOCUMENTATION.org
Thank you 👍
Cherry-picked into develop branch, you can safely delete your branch.