New layer variable `dotspacemacs-mode-line-themes`:
Set the theme for the Spaceline. Supported themes are `spacemacs',
`all-the-icons', `custom', `vim-powerline' and `vanilla'. The first three
are spaceline themes. `vanilla' is default Emacs mode-line. `custom' is a
user defined themes, refer to the DOCUMENTATION.org for more info on how
to create your own spaceline theme."
See DOCUMENTATION.org changes for more info.
This commit adds support for `spaceline-all-the-icons` package.
