Add two new functions: `spacemacs/transient-state-register-add-bindings`
and `spacemacs/transient-state-register-remove-bindings` to prevent layer
authors and end users from dealing with the underlying variables' subtleties.
Highlight should already be done automatocally.
This highlight is not desirable because it breaks `n` and `N` search of
occurences and it breaks `:nohl:` as well making it impossible to revert an
highlighted word.
These drawbacks were maybe intentional since it was about highlighting
_permanently_ but it goes against principle of least astonishement, users will
be consufed about an highlight that cannot be reverted whatsoever.
We need an highlighting facility in Spacemacs, there was one at some point with
the package `hl-anything` but at the time it was buggy and removed from
Spacemacs (see layer spacemacs-editing-visual). Maybe we could try it again.
Create new layers:
- spacemacs-navigation: contains packages whose principal goal is navigation
- spacemacs-modeline: contains packages about mode line
Merge spacemacs-ui and spacemacs-ui-visual into layer spacemacs-visual.
