Useful when debugging why the keyboard doesn't work as expected with a
specific app.

Instead of a fixed size that don't work at all for bigger screens.

Other tweaks:
- Use the value-land dimens to vary 'extra_horizontal_margin'
- Move label size to Config, because it can change at runtime (rotation)
- Slightly decrease the size of "long" symbols

Depending on the pixel density isn't ideal for a keyboard, which would
render differently depending on the "scaling" accessibility option.

Landscape mode needs a special values. At the same time, increase the
horizontal margin when landscape.

Also, draw activated keys with a round border too.

Themes replace 'colors.xml' and soon will replace 'dimens.xml'.

Use xmllint.
Re-indent Java files using spaces.

Increase a bit labels size and reduce empty space between keys.

This was a half-finished feature:
- Dangerous when typing passwords
- Caused crash on some devices
- Ugly (on its own but also blinking when sliding and not fixed in size)